cmd/go: remove subcommand prefix from error messages

For example, errors that started before with "go mod download: " now
start with "go: " instead.

Previously, we had a mix of errors with and without subcommand
prefixes, even in packages like modload that ostensibly aren't tied
to any specific command. This change makes usage more consistent,
which makes refactoring much easier.

These prefixes didn't add useful information: the user should know the
subcommand they just ran. But see CL 347152 for an attempt at making
the opposite change: always printing the subcommand prefix.

Note that there are a number of errors that don't start with "go: " or
any subcommand prefix. This CL doesn't affect those.

Change-Id: I16430d8c39ea3f4d0870f55a5205f06fb21943c0
Reviewed-on: https://go-review.googlesource.com/c/go/+/349597
Trust: Jay Conrod <jayconrod@google.com>
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
diff --git a/src/cmd/go/internal/base/tool.go b/src/cmd/go/internal/base/tool.go
index d0da65e..f927016 100644
--- a/src/cmd/go/internal/base/tool.go
+++ b/src/cmd/go/internal/base/tool.go
@@ -36,7 +36,7 @@
 	}
 	// Give a nice message if there is no tool with that name.
 	if _, err := os.Stat(toolPath); err != nil {
-		fmt.Fprintf(os.Stderr, "go tool: no such tool %q\n", toolName)
+		fmt.Fprintf(os.Stderr, "go: no such tool %q\n", toolName)
 		SetExitStatus(2)
 		Exit()
 	}
diff --git a/src/cmd/go/internal/bug/bug.go b/src/cmd/go/internal/bug/bug.go
index 307527c..a81ca7d 100644
--- a/src/cmd/go/internal/bug/bug.go
+++ b/src/cmd/go/internal/bug/bug.go
@@ -40,7 +40,7 @@
 
 func runBug(ctx context.Context, cmd *base.Command, args []string) {
 	if len(args) > 0 {
-		base.Fatalf("go bug: bug takes no arguments")
+		base.Fatalf("go: bug takes no arguments")
 	}
 	var buf bytes.Buffer
 	buf.WriteString(bugHeader)
diff --git a/src/cmd/go/internal/clean/clean.go b/src/cmd/go/internal/clean/clean.go
index fd4cb20..1089211 100644
--- a/src/cmd/go/internal/clean/clean.go
+++ b/src/cmd/go/internal/clean/clean.go
@@ -144,7 +144,7 @@
 						// This also mimics what os.RemoveAll(dir) would do.
 						if err := os.RemoveAll(d); err != nil && !printedErrors {
 							printedErrors = true
-							base.Errorf("go clean -cache: %v", err)
+							base.Errorf("go: %v", err)
 						}
 					}
 				}
@@ -157,7 +157,7 @@
 			if !cfg.BuildN {
 				if err := os.RemoveAll(logFile); err != nil && !printedErrors {
 					printedErrors = true
-					base.Errorf("go clean -cache: %v", err)
+					base.Errorf("go: %v", err)
 				}
 			}
 		}
@@ -187,7 +187,7 @@
 			}
 			if err != nil {
 				if _, statErr := os.Stat(dir); !os.IsNotExist(statErr) {
-					base.Errorf("go clean -testcache: %v", err)
+					base.Errorf("go: %v", err)
 				}
 			}
 		}
@@ -195,14 +195,14 @@
 
 	if cleanModcache {
 		if cfg.GOMODCACHE == "" {
-			base.Fatalf("go clean -modcache: no module cache")
+			base.Fatalf("go: cannot clean -modcache without a module cache")
 		}
 		if cfg.BuildN || cfg.BuildX {
 			b.Showcmd("", "rm -rf %s", cfg.GOMODCACHE)
 		}
 		if !cfg.BuildN {
 			if err := modfetch.RemoveAll(cfg.GOMODCACHE); err != nil {
-				base.Errorf("go clean -modcache: %v", err)
+				base.Errorf("go: %v", err)
 			}
 		}
 	}
@@ -245,7 +245,7 @@
 	}
 	dirs, err := os.ReadDir(p.Dir)
 	if err != nil {
-		base.Errorf("go clean %s: %v", p.Dir, err)
+		base.Errorf("go: %s: %v", p.Dir, err)
 		return
 	}
 
@@ -334,7 +334,7 @@
 					}
 				}
 				if err := os.RemoveAll(filepath.Join(p.Dir, name)); err != nil {
-					base.Errorf("go clean: %v", err)
+					base.Errorf("go: %v", err)
 				}
 			}
 			continue
@@ -386,5 +386,5 @@
 			return
 		}
 	}
-	base.Errorf("go clean: %v", err)
+	base.Errorf("go: %v", err)
 }
diff --git a/src/cmd/go/internal/envcmd/env.go b/src/cmd/go/internal/envcmd/env.go
index d23d539..1eb7734 100644
--- a/src/cmd/go/internal/envcmd/env.go
+++ b/src/cmd/go/internal/envcmd/env.go
@@ -193,13 +193,13 @@
 
 func runEnv(ctx context.Context, cmd *base.Command, args []string) {
 	if *envJson && *envU {
-		base.Fatalf("go env: cannot use -json with -u")
+		base.Fatalf("go: cannot use -json with -u")
 	}
 	if *envJson && *envW {
-		base.Fatalf("go env: cannot use -json with -w")
+		base.Fatalf("go: cannot use -json with -w")
 	}
 	if *envU && *envW {
-		base.Fatalf("go env: cannot use -u with -w")
+		base.Fatalf("go: cannot use -u with -w")
 	}
 
 	// Handle 'go env -w' and 'go env -u' before calling buildcfg.Check,
@@ -277,7 +277,7 @@
 func runEnvW(args []string) {
 	// Process and sanity-check command line.
 	if len(args) == 0 {
-		base.Fatalf("go env -w: no KEY=VALUE arguments given")
+		base.Fatalf("go: no KEY=VALUE arguments given")
 	}
 	osEnv := make(map[string]string)
 	for _, e := range cfg.OrigEnv {
@@ -289,14 +289,14 @@
 	for _, arg := range args {
 		i := strings.Index(arg, "=")
 		if i < 0 {
-			base.Fatalf("go env -w: arguments must be KEY=VALUE: invalid argument: %s", arg)
+			base.Fatalf("go: arguments must be KEY=VALUE: invalid argument: %s", arg)
 		}
 		key, val := arg[:i], arg[i+1:]
 		if err := checkEnvWrite(key, val); err != nil {
-			base.Fatalf("go env -w: %v", err)
+			base.Fatalf("go: %v", err)
 		}
 		if _, ok := add[key]; ok {
-			base.Fatalf("go env -w: multiple values for key: %s", key)
+			base.Fatalf("go: multiple values for key: %s", key)
 		}
 		add[key] = val
 		if osVal := osEnv[key]; osVal != "" && osVal != val {
@@ -305,13 +305,13 @@
 	}
 
 	if err := checkBuildConfig(add, nil); err != nil {
-		base.Fatalf("go env -w: %v", err)
+		base.Fatalf("go: %v", err)
 	}
 
 	gotmp, okGOTMP := add["GOTMPDIR"]
 	if okGOTMP {
 		if !filepath.IsAbs(gotmp) && gotmp != "" {
-			base.Fatalf("go env -w: GOTMPDIR must be an absolute path")
+			base.Fatalf("go: GOTMPDIR must be an absolute path")
 		}
 	}
 
@@ -321,18 +321,18 @@
 func runEnvU(args []string) {
 	// Process and sanity-check command line.
 	if len(args) == 0 {
-		base.Fatalf("go env -u: no arguments given")
+		base.Fatalf("go: 'go env -u' requires an argument")
 	}
 	del := make(map[string]bool)
 	for _, arg := range args {
 		if err := checkEnvWrite(arg, ""); err != nil {
-			base.Fatalf("go env -u: %v", err)
+			base.Fatalf("go: %v", err)
 		}
 		del[arg] = true
 	}
 
 	if err := checkBuildConfig(nil, del); err != nil {
-		base.Fatalf("go env -u: %v", err)
+		base.Fatalf("go: %v", err)
 	}
 
 	updateEnvFile(nil, del)
@@ -416,7 +416,7 @@
 	enc := json.NewEncoder(os.Stdout)
 	enc.SetIndent("", "\t")
 	if err := enc.Encode(m); err != nil {
-		base.Fatalf("go env -json: %s", err)
+		base.Fatalf("go: %s", err)
 	}
 }
 
@@ -494,11 +494,11 @@
 func updateEnvFile(add map[string]string, del map[string]bool) {
 	file, err := cfg.EnvFile()
 	if file == "" {
-		base.Fatalf("go env: cannot find go env config: %v", err)
+		base.Fatalf("go: cannot find go env config: %v", err)
 	}
 	data, err := os.ReadFile(file)
 	if err != nil && (!os.IsNotExist(err) || len(add) == 0) {
-		base.Fatalf("go env: reading go env config: %v", err)
+		base.Fatalf("go: reading go env config: %v", err)
 	}
 
 	lines := strings.SplitAfter(string(data), "\n")
@@ -556,7 +556,7 @@
 		os.MkdirAll(filepath.Dir(file), 0777)
 		err = os.WriteFile(file, data, 0666)
 		if err != nil {
-			base.Fatalf("go env: writing go env config: %v", err)
+			base.Fatalf("go: writing go env config: %v", err)
 		}
 	}
 }
diff --git a/src/cmd/go/internal/get/get.go b/src/cmd/go/internal/get/get.go
index 075594b..b79d3ba 100644
--- a/src/cmd/go/internal/get/get.go
+++ b/src/cmd/go/internal/get/get.go
@@ -114,16 +114,16 @@
 func runGet(ctx context.Context, cmd *base.Command, args []string) {
 	if cfg.ModulesEnabled {
 		// Should not happen: main.go should install the separate module-enabled get code.
-		base.Fatalf("go get: modules not implemented")
+		base.Fatalf("go: modules not implemented")
 	}
 
 	work.BuildInit()
 
 	if *getF && !*getU {
-		base.Fatalf("go get: cannot use -f flag without -u")
+		base.Fatalf("go: cannot use -f flag without -u")
 	}
 	if *getInsecure {
-		base.Fatalf("go get: -insecure flag is no longer supported; use GOINSECURE instead")
+		base.Fatalf("go: -insecure flag is no longer supported; use GOINSECURE instead")
 	}
 
 	// Disable any prompting for passwords by Git itself.
@@ -214,11 +214,11 @@
 		// if the argument has no slash or refers to an existing file.
 		if strings.HasSuffix(arg, ".go") {
 			if !strings.Contains(arg, "/") {
-				base.Errorf("go get %s: arguments must be package or module paths", arg)
+				base.Errorf("go: %s: arguments must be package or module paths", arg)
 				continue
 			}
 			if fi, err := os.Stat(arg); err == nil && !fi.IsDir() {
-				base.Errorf("go get: %s exists as a file, but 'go get' requires package arguments", arg)
+				base.Errorf("go: %s exists as a file, but 'go get' requires package arguments", arg)
 			}
 		}
 	}
diff --git a/src/cmd/go/internal/list/list.go b/src/cmd/go/internal/list/list.go
index 704d61e..821e622 100644
--- a/src/cmd/go/internal/list/list.go
+++ b/src/cmd/go/internal/list/list.go
@@ -427,12 +427,12 @@
 		}
 
 		if modload.Init(); !modload.Enabled() {
-			base.Fatalf("go list -m: not using modules")
+			base.Fatalf("go: list -m cannot be used with GO111MODULE=off")
 		}
 
 		modload.LoadModFile(ctx) // Sets cfg.BuildMod as a side-effect.
 		if cfg.BuildMod == "vendor" {
-			const actionDisabledFormat = "go list -m: can't %s using the vendor directory\n\t(Use -mod=mod or -mod=readonly to bypass.)"
+			const actionDisabledFormat = "go: can't %s using the vendor directory\n\t(Use -mod=mod or -mod=readonly to bypass.)"
 
 			if *listVersions {
 				base.Fatalf(actionDisabledFormat, "determine available versions")
@@ -471,11 +471,11 @@
 		if !*listE {
 			for _, m := range mods {
 				if m.Error != nil {
-					base.Errorf("go list -m: %v", m.Error.Err)
+					base.Errorf("go: %v", m.Error.Err)
 				}
 			}
 			if err != nil {
-				base.Errorf("go list -m: %v", err)
+				base.Errorf("go: %v", err)
 			}
 			base.ExitIfErrors()
 		}
@@ -711,7 +711,7 @@
 			}
 			rmods, err := modload.ListModules(ctx, args, mode)
 			if err != nil && !*listE {
-				base.Errorf("go list -retracted: %v", err)
+				base.Errorf("go: %v", err)
 			}
 			for i, arg := range args {
 				rmod := rmods[i]
diff --git a/src/cmd/go/internal/modcmd/download.go b/src/cmd/go/internal/modcmd/download.go
index ff56d05..0f64785 100644
--- a/src/cmd/go/internal/modcmd/download.go
+++ b/src/cmd/go/internal/modcmd/download.go
@@ -87,7 +87,7 @@
 	// Check whether modules are enabled and whether we're in a module.
 	modload.ForceUseModules = true
 	if !modload.HasModRoot() && len(args) == 0 {
-		base.Fatalf("go mod download: no modules specified (see 'go help mod download')")
+		base.Fatalf("go: no modules specified (see 'go help mod download')")
 	}
 	haveExplicitArgs := len(args) > 0
 	if !haveExplicitArgs {
@@ -106,7 +106,7 @@
 		for _, arg := range args {
 			switch arg {
 			case mainModule.Path, targetAtUpgrade, targetAtPatch:
-				os.Stderr.WriteString("go mod download: skipping argument " + arg + " that resolves to the main module\n")
+				os.Stderr.WriteString("go: skipping download of " + arg + " that resolves to the main module\n")
 			}
 		}
 	}
@@ -192,7 +192,7 @@
 		for _, m := range mods {
 			b, err := json.MarshalIndent(m, "", "\t")
 			if err != nil {
-				base.Fatalf("go mod download: %v", err)
+				base.Fatalf("go: %v", err)
 			}
 			os.Stdout.Write(append(b, '\n'))
 			if m.Error != "" {
@@ -202,7 +202,7 @@
 	} else {
 		for _, m := range mods {
 			if m.Error != "" {
-				base.Errorf("go mod download: %v", m.Error)
+				base.Errorf("go: %v", m.Error)
 			}
 		}
 		base.ExitIfErrors()
@@ -222,6 +222,6 @@
 	// (after we've written the checksums for the modules that were downloaded
 	// successfully).
 	if infosErr != nil {
-		base.Errorf("go mod download: %v", infosErr)
+		base.Errorf("go: %v", infosErr)
 	}
 }
diff --git a/src/cmd/go/internal/modcmd/edit.go b/src/cmd/go/internal/modcmd/edit.go
index bb3d521..e5182a9 100644
--- a/src/cmd/go/internal/modcmd/edit.go
+++ b/src/cmd/go/internal/modcmd/edit.go
@@ -171,15 +171,15 @@
 			len(edits) > 0
 
 	if !anyFlags {
-		base.Fatalf("go mod edit: no flags specified (see 'go help mod edit').")
+		base.Fatalf("go: no flags specified (see 'go help mod edit').")
 	}
 
 	if *editJSON && *editPrint {
-		base.Fatalf("go mod edit: cannot use both -json and -print")
+		base.Fatalf("go: cannot use both -json and -print")
 	}
 
 	if len(args) > 1 {
-		base.Fatalf("go mod edit: too many arguments")
+		base.Fatalf("go: too many arguments")
 	}
 	var gomod string
 	if len(args) == 1 {
@@ -190,7 +190,7 @@
 
 	if *editModule != "" {
 		if err := module.CheckImportPath(*editModule); err != nil {
-			base.Fatalf("go mod: invalid -module: %v", err)
+			base.Fatalf("go: invalid -module: %v", err)
 		}
 	}
 
@@ -264,15 +264,15 @@
 func parsePathVersion(flag, arg string) (path, version string) {
 	i := strings.Index(arg, "@")
 	if i < 0 {
-		base.Fatalf("go mod: -%s=%s: need path@version", flag, arg)
+		base.Fatalf("go: -%s=%s: need path@version", flag, arg)
 	}
 	path, version = strings.TrimSpace(arg[:i]), strings.TrimSpace(arg[i+1:])
 	if err := module.CheckImportPath(path); err != nil {
-		base.Fatalf("go mod: -%s=%s: invalid path: %v", flag, arg, err)
+		base.Fatalf("go: -%s=%s: invalid path: %v", flag, arg, err)
 	}
 
 	if !allowedVersionArg(version) {
-		base.Fatalf("go mod: -%s=%s: invalid version %q", flag, arg, version)
+		base.Fatalf("go: -%s=%s: invalid version %q", flag, arg, version)
 	}
 
 	return path, version
@@ -281,11 +281,11 @@
 // parsePath parses -flag=arg expecting arg to be path (not path@version).
 func parsePath(flag, arg string) (path string) {
 	if strings.Contains(arg, "@") {
-		base.Fatalf("go mod: -%s=%s: need just path, not path@version", flag, arg)
+		base.Fatalf("go: -%s=%s: need just path, not path@version", flag, arg)
 	}
 	path = arg
 	if err := module.CheckImportPath(path); err != nil {
-		base.Fatalf("go mod: -%s=%s: invalid path: %v", flag, arg, err)
+		base.Fatalf("go: -%s=%s: invalid path: %v", flag, arg, err)
 	}
 	return path
 }
@@ -350,7 +350,7 @@
 	path, version := parsePathVersion("require", arg)
 	edits = append(edits, func(f *modfile.File) {
 		if err := f.AddRequire(path, version); err != nil {
-			base.Fatalf("go mod: -require=%s: %v", arg, err)
+			base.Fatalf("go: -require=%s: %v", arg, err)
 		}
 	})
 }
@@ -360,7 +360,7 @@
 	path := parsePath("droprequire", arg)
 	edits = append(edits, func(f *modfile.File) {
 		if err := f.DropRequire(path); err != nil {
-			base.Fatalf("go mod: -droprequire=%s: %v", arg, err)
+			base.Fatalf("go: -droprequire=%s: %v", arg, err)
 		}
 	})
 }
@@ -370,7 +370,7 @@
 	path, version := parsePathVersion("exclude", arg)
 	edits = append(edits, func(f *modfile.File) {
 		if err := f.AddExclude(path, version); err != nil {
-			base.Fatalf("go mod: -exclude=%s: %v", arg, err)
+			base.Fatalf("go: -exclude=%s: %v", arg, err)
 		}
 	})
 }
@@ -380,7 +380,7 @@
 	path, version := parsePathVersion("dropexclude", arg)
 	edits = append(edits, func(f *modfile.File) {
 		if err := f.DropExclude(path, version); err != nil {
-			base.Fatalf("go mod: -dropexclude=%s: %v", arg, err)
+			base.Fatalf("go: -dropexclude=%s: %v", arg, err)
 		}
 	})
 }
@@ -389,27 +389,27 @@
 func flagReplace(arg string) {
 	var i int
 	if i = strings.Index(arg, "="); i < 0 {
-		base.Fatalf("go mod: -replace=%s: need old[@v]=new[@w] (missing =)", arg)
+		base.Fatalf("go: -replace=%s: need old[@v]=new[@w] (missing =)", arg)
 	}
 	old, new := strings.TrimSpace(arg[:i]), strings.TrimSpace(arg[i+1:])
 	if strings.HasPrefix(new, ">") {
-		base.Fatalf("go mod: -replace=%s: separator between old and new is =, not =>", arg)
+		base.Fatalf("go: -replace=%s: separator between old and new is =, not =>", arg)
 	}
 	oldPath, oldVersion, err := parsePathVersionOptional("old", old, false)
 	if err != nil {
-		base.Fatalf("go mod: -replace=%s: %v", arg, err)
+		base.Fatalf("go: -replace=%s: %v", arg, err)
 	}
 	newPath, newVersion, err := parsePathVersionOptional("new", new, true)
 	if err != nil {
-		base.Fatalf("go mod: -replace=%s: %v", arg, err)
+		base.Fatalf("go: -replace=%s: %v", arg, err)
 	}
 	if newPath == new && !modfile.IsDirectoryPath(new) {
-		base.Fatalf("go mod: -replace=%s: unversioned new path must be local directory", arg)
+		base.Fatalf("go: -replace=%s: unversioned new path must be local directory", arg)
 	}
 
 	edits = append(edits, func(f *modfile.File) {
 		if err := f.AddReplace(oldPath, oldVersion, newPath, newVersion); err != nil {
-			base.Fatalf("go mod: -replace=%s: %v", arg, err)
+			base.Fatalf("go: -replace=%s: %v", arg, err)
 		}
 	})
 }
@@ -418,11 +418,11 @@
 func flagDropReplace(arg string) {
 	path, version, err := parsePathVersionOptional("old", arg, true)
 	if err != nil {
-		base.Fatalf("go mod: -dropreplace=%s: %v", arg, err)
+		base.Fatalf("go: -dropreplace=%s: %v", arg, err)
 	}
 	edits = append(edits, func(f *modfile.File) {
 		if err := f.DropReplace(path, version); err != nil {
-			base.Fatalf("go mod: -dropreplace=%s: %v", arg, err)
+			base.Fatalf("go: -dropreplace=%s: %v", arg, err)
 		}
 	})
 }
@@ -431,11 +431,11 @@
 func flagRetract(arg string) {
 	vi, err := parseVersionInterval(arg)
 	if err != nil {
-		base.Fatalf("go mod: -retract=%s: %v", arg, err)
+		base.Fatalf("go: -retract=%s: %v", arg, err)
 	}
 	edits = append(edits, func(f *modfile.File) {
 		if err := f.AddRetract(vi, ""); err != nil {
-			base.Fatalf("go mod: -retract=%s: %v", arg, err)
+			base.Fatalf("go: -retract=%s: %v", arg, err)
 		}
 	})
 }
@@ -444,11 +444,11 @@
 func flagDropRetract(arg string) {
 	vi, err := parseVersionInterval(arg)
 	if err != nil {
-		base.Fatalf("go mod: -dropretract=%s: %v", arg, err)
+		base.Fatalf("go: -dropretract=%s: %v", arg, err)
 	}
 	edits = append(edits, func(f *modfile.File) {
 		if err := f.DropRetract(vi); err != nil {
-			base.Fatalf("go mod: -dropretract=%s: %v", arg, err)
+			base.Fatalf("go: -dropretract=%s: %v", arg, err)
 		}
 	})
 }
diff --git a/src/cmd/go/internal/modcmd/editwork.go b/src/cmd/go/internal/modcmd/editwork.go
index 29895b1..235c655 100644
--- a/src/cmd/go/internal/modcmd/editwork.go
+++ b/src/cmd/go/internal/modcmd/editwork.go
@@ -118,15 +118,15 @@
 			len(workedits) > 0
 
 	if !anyFlags {
-		base.Fatalf("go mod edit: no flags specified (see 'go help mod edit').")
+		base.Fatalf("go: no flags specified (see 'go help mod edit').")
 	}
 
 	if *editworkJSON && *editworkPrint {
-		base.Fatalf("go mod edit: cannot use both -json and -print")
+		base.Fatalf("go: cannot use both -json and -print")
 	}
 
 	if len(args) > 1 {
-		base.Fatalf("go mod edit: too many arguments")
+		base.Fatalf("go: 'go mod editwork' accepts at most one argument")
 	}
 	var gowork string
 	if len(args) == 1 {
@@ -199,7 +199,7 @@
 		}
 		f.AddDirectory(modload.ToDirectoryPath(arg), modulePath)
 		if err := f.AddDirectory(modload.ToDirectoryPath(arg), ""); err != nil {
-			base.Fatalf("go mod: -directory=%s: %v", arg, err)
+			base.Fatalf("go: -directory=%s: %v", arg, err)
 		}
 	})
 }
@@ -208,7 +208,7 @@
 func flagEditworkDropDirectory(arg string) {
 	workedits = append(workedits, func(f *modfile.WorkFile) {
 		if err := f.DropDirectory(modload.ToDirectoryPath(arg)); err != nil {
-			base.Fatalf("go mod: -dropdirectory=%s: %v", arg, err)
+			base.Fatalf("go: -dropdirectory=%s: %v", arg, err)
 		}
 	})
 }
@@ -217,27 +217,27 @@
 func flagEditworkReplace(arg string) {
 	var i int
 	if i = strings.Index(arg, "="); i < 0 {
-		base.Fatalf("go mod: -replace=%s: need old[@v]=new[@w] (missing =)", arg)
+		base.Fatalf("go: -replace=%s: need old[@v]=new[@w] (missing =)", arg)
 	}
 	old, new := strings.TrimSpace(arg[:i]), strings.TrimSpace(arg[i+1:])
 	if strings.HasPrefix(new, ">") {
-		base.Fatalf("go mod: -replace=%s: separator between old and new is =, not =>", arg)
+		base.Fatalf("go: -replace=%s: separator between old and new is =, not =>", arg)
 	}
 	oldPath, oldVersion, err := parsePathVersionOptional("old", old, false)
 	if err != nil {
-		base.Fatalf("go mod: -replace=%s: %v", arg, err)
+		base.Fatalf("go: -replace=%s: %v", arg, err)
 	}
 	newPath, newVersion, err := parsePathVersionOptional("new", new, true)
 	if err != nil {
-		base.Fatalf("go mod: -replace=%s: %v", arg, err)
+		base.Fatalf("go: -replace=%s: %v", arg, err)
 	}
 	if newPath == new && !modfile.IsDirectoryPath(new) {
-		base.Fatalf("go mod: -replace=%s: unversioned new path must be local directory", arg)
+		base.Fatalf("go: -replace=%s: unversioned new path must be local directory", arg)
 	}
 
 	workedits = append(workedits, func(f *modfile.WorkFile) {
 		if err := f.AddReplace(oldPath, oldVersion, newPath, newVersion); err != nil {
-			base.Fatalf("go mod: -replace=%s: %v", arg, err)
+			base.Fatalf("go: -replace=%s: %v", arg, err)
 		}
 	})
 }
@@ -246,11 +246,11 @@
 func flagEditworkDropReplace(arg string) {
 	path, version, err := parsePathVersionOptional("old", arg, true)
 	if err != nil {
-		base.Fatalf("go mod: -dropreplace=%s: %v", arg, err)
+		base.Fatalf("go: -dropreplace=%s: %v", arg, err)
 	}
 	workedits = append(workedits, func(f *modfile.WorkFile) {
 		if err := f.DropReplace(path, version); err != nil {
-			base.Fatalf("go mod: -dropreplace=%s: %v", arg, err)
+			base.Fatalf("go: -dropreplace=%s: %v", arg, err)
 		}
 	})
 }
diff --git a/src/cmd/go/internal/modcmd/graph.go b/src/cmd/go/internal/modcmd/graph.go
index 2cbabae..9b6aa1f 100644
--- a/src/cmd/go/internal/modcmd/graph.go
+++ b/src/cmd/go/internal/modcmd/graph.go
@@ -49,7 +49,7 @@
 	modload.InitWorkfile()
 
 	if len(args) > 0 {
-		base.Fatalf("go mod graph: graph takes no arguments")
+		base.Fatalf("go: 'go mod graph' accepts no arguments")
 	}
 	modload.ForceUseModules = true
 	modload.RootMode = modload.NeedRoot
diff --git a/src/cmd/go/internal/modcmd/init.go b/src/cmd/go/internal/modcmd/init.go
index 958c306..bc4620a 100644
--- a/src/cmd/go/internal/modcmd/init.go
+++ b/src/cmd/go/internal/modcmd/init.go
@@ -39,7 +39,7 @@
 
 func runInit(ctx context.Context, cmd *base.Command, args []string) {
 	if len(args) > 1 {
-		base.Fatalf("go mod init: too many arguments")
+		base.Fatalf("go: 'go mod init' accepts at most one argument")
 	}
 	var modPath string
 	if len(args) == 1 {
diff --git a/src/cmd/go/internal/modcmd/tidy.go b/src/cmd/go/internal/modcmd/tidy.go
index fe25507..57d303a 100644
--- a/src/cmd/go/internal/modcmd/tidy.go
+++ b/src/cmd/go/internal/modcmd/tidy.go
@@ -95,7 +95,7 @@
 
 func runTidy(ctx context.Context, cmd *base.Command, args []string) {
 	if len(args) > 0 {
-		base.Fatalf("go mod tidy: no arguments allowed")
+		base.Fatalf("go: 'go mod tidy' accepts no arguments")
 	}
 
 	// Tidy aims to make 'go test' reproducible for any package in 'all', so we
diff --git a/src/cmd/go/internal/modcmd/vendor.go b/src/cmd/go/internal/modcmd/vendor.go
index 1effcea..92348b8 100644
--- a/src/cmd/go/internal/modcmd/vendor.go
+++ b/src/cmd/go/internal/modcmd/vendor.go
@@ -59,7 +59,7 @@
 
 func runVendor(ctx context.Context, cmd *base.Command, args []string) {
 	if len(args) != 0 {
-		base.Fatalf("go mod vendor: vendor takes no arguments")
+		base.Fatalf("go: 'go mod vendor' accepts no arguments")
 	}
 	modload.ForceUseModules = true
 	modload.RootMode = modload.NeedRoot
@@ -76,7 +76,7 @@
 
 	vdir := filepath.Join(modload.VendorDir())
 	if err := os.RemoveAll(vdir); err != nil {
-		base.Fatalf("go mod vendor: %v", err)
+		base.Fatalf("go: %v", err)
 	}
 
 	modpkgs := make(map[module.Version][]string)
@@ -178,11 +178,11 @@
 	}
 
 	if err := os.MkdirAll(vdir, 0777); err != nil {
-		base.Fatalf("go mod vendor: %v", err)
+		base.Fatalf("go: %v", err)
 	}
 
 	if err := os.WriteFile(filepath.Join(vdir, "modules.txt"), buf.Bytes(), 0666); err != nil {
-		base.Fatalf("go mod vendor: %v", err)
+		base.Fatalf("go: %v", err)
 	}
 }
 
@@ -250,7 +250,7 @@
 	embedPatterns := str.StringList(bp.EmbedPatterns, bp.TestEmbedPatterns, bp.XTestEmbedPatterns)
 	embeds, err := load.ResolveEmbed(bp.Dir, embedPatterns)
 	if err != nil {
-		base.Fatalf("go mod vendor: %v", err)
+		base.Fatalf("go: %v", err)
 	}
 	for _, embed := range embeds {
 		embedDst := filepath.Join(dst, embed)
@@ -261,21 +261,21 @@
 		// Copy the file as is done by copyDir below.
 		r, err := os.Open(filepath.Join(src, embed))
 		if err != nil {
-			base.Fatalf("go mod vendor: %v", err)
+			base.Fatalf("go: %v", err)
 		}
 		if err := os.MkdirAll(filepath.Dir(embedDst), 0777); err != nil {
-			base.Fatalf("go mod vendor: %v", err)
+			base.Fatalf("go: %v", err)
 		}
 		w, err := os.Create(embedDst)
 		if err != nil {
-			base.Fatalf("go mod vendor: %v", err)
+			base.Fatalf("go: %v", err)
 		}
 		if _, err := io.Copy(w, r); err != nil {
-			base.Fatalf("go mod vendor: %v", err)
+			base.Fatalf("go: %v", err)
 		}
 		r.Close()
 		if err := w.Close(); err != nil {
-			base.Fatalf("go mod vendor: %v", err)
+			base.Fatalf("go: %v", err)
 		}
 	}
 }
@@ -354,7 +354,7 @@
 	if strings.HasSuffix(info.Name(), ".go") {
 		f, err := fsys.Open(filepath.Join(dir, info.Name()))
 		if err != nil {
-			base.Fatalf("go mod vendor: %v", err)
+			base.Fatalf("go: %v", err)
 		}
 		defer f.Close()
 
@@ -376,10 +376,10 @@
 func copyDir(dst, src string, match func(dir string, info fs.DirEntry) bool, copiedFiles map[string]bool) {
 	files, err := os.ReadDir(src)
 	if err != nil {
-		base.Fatalf("go mod vendor: %v", err)
+		base.Fatalf("go: %v", err)
 	}
 	if err := os.MkdirAll(dst, 0777); err != nil {
-		base.Fatalf("go mod vendor: %v", err)
+		base.Fatalf("go: %v", err)
 	}
 	for _, file := range files {
 		if file.IsDir() || !file.Type().IsRegular() || !match(src, file) {
@@ -388,20 +388,20 @@
 		copiedFiles[file.Name()] = true
 		r, err := os.Open(filepath.Join(src, file.Name()))
 		if err != nil {
-			base.Fatalf("go mod vendor: %v", err)
+			base.Fatalf("go: %v", err)
 		}
 		dstPath := filepath.Join(dst, file.Name())
 		copiedFiles[dstPath] = true
 		w, err := os.Create(dstPath)
 		if err != nil {
-			base.Fatalf("go mod vendor: %v", err)
+			base.Fatalf("go: %v", err)
 		}
 		if _, err := io.Copy(w, r); err != nil {
-			base.Fatalf("go mod vendor: %v", err)
+			base.Fatalf("go: %v", err)
 		}
 		r.Close()
 		if err := w.Close(); err != nil {
-			base.Fatalf("go mod vendor: %v", err)
+			base.Fatalf("go: %v", err)
 		}
 	}
 }
diff --git a/src/cmd/go/internal/modcmd/verify.go b/src/cmd/go/internal/modcmd/verify.go
index 14c4d76..3f0c005 100644
--- a/src/cmd/go/internal/modcmd/verify.go
+++ b/src/cmd/go/internal/modcmd/verify.go
@@ -47,7 +47,7 @@
 
 	if len(args) != 0 {
 		// NOTE(rsc): Could take a module pattern.
-		base.Fatalf("go mod verify: verify takes no arguments")
+		base.Fatalf("go: verify takes no arguments")
 	}
 	modload.ForceUseModules = true
 	modload.RootMode = modload.NeedRoot
diff --git a/src/cmd/go/internal/modcmd/why.go b/src/cmd/go/internal/modcmd/why.go
index eef5fa5..ed5e9d7 100644
--- a/src/cmd/go/internal/modcmd/why.go
+++ b/src/cmd/go/internal/modcmd/why.go
@@ -80,13 +80,13 @@
 	if *whyM {
 		for _, arg := range args {
 			if strings.Contains(arg, "@") {
-				base.Fatalf("go mod why: module query not allowed")
+				base.Fatalf("go: %s: 'go mod why' requires a module path, not a version query", arg)
 			}
 		}
 
 		mods, err := modload.ListModules(ctx, args, 0)
 		if err != nil {
-			base.Fatalf("go mod why: %v", err)
+			base.Fatalf("go: %v", err)
 		}
 
 		byModule := make(map[module.Version][]string)
diff --git a/src/cmd/go/internal/modget/get.go b/src/cmd/go/internal/modget/get.go
index 37912ce..db07624 100644
--- a/src/cmd/go/internal/modget/get.go
+++ b/src/cmd/go/internal/modget/get.go
@@ -263,19 +263,19 @@
 	case "", "upgrade", "patch":
 		// ok
 	default:
-		base.Fatalf("go get: unknown upgrade flag -u=%s", getU.rawVersion)
+		base.Fatalf("go: unknown upgrade flag -u=%s", getU.rawVersion)
 	}
 	if *getF {
-		fmt.Fprintf(os.Stderr, "go get: -f flag is a no-op when using modules\n")
+		fmt.Fprintf(os.Stderr, "go: -f flag is a no-op when using modules\n")
 	}
 	if *getFix {
-		fmt.Fprintf(os.Stderr, "go get: -fix flag is a no-op when using modules\n")
+		fmt.Fprintf(os.Stderr, "go: -fix flag is a no-op when using modules\n")
 	}
 	if *getM {
-		base.Fatalf("go get: -m flag is no longer supported; consider -d to skip building packages")
+		base.Fatalf("go: -m flag is no longer supported; consider -d to skip building packages")
 	}
 	if *getInsecure {
-		base.Fatalf("go get: -insecure flag is no longer supported; use GOINSECURE instead")
+		base.Fatalf("go: -insecure flag is no longer supported; use GOINSECURE instead")
 	}
 
 	// Do not allow any updating of go.mod until we've applied
@@ -397,7 +397,7 @@
 			}
 		}
 		if haveExternalExe {
-			fmt.Fprint(os.Stderr, "go get: installing executables with 'go get' in module mode is deprecated.")
+			fmt.Fprint(os.Stderr, "go: installing executables with 'go get' in module mode is deprecated.")
 			var altMsg string
 			if modload.HasModRoot() {
 				altMsg = `
@@ -442,7 +442,7 @@
 	for _, arg := range search.CleanPatterns(rawArgs) {
 		q, err := newQuery(arg)
 		if err != nil {
-			base.Errorf("go get: %v", err)
+			base.Errorf("go: %v", err)
 			continue
 		}
 
@@ -457,11 +457,11 @@
 		// if the argument has no version and either has no slash or refers to an existing file.
 		if strings.HasSuffix(q.raw, ".go") && q.rawVersion == "" {
 			if !strings.Contains(q.raw, "/") {
-				base.Errorf("go get %s: arguments must be package or module paths", q.raw)
+				base.Errorf("go: %s: arguments must be package or module paths", q.raw)
 				continue
 			}
 			if fi, err := os.Stat(q.raw); err == nil && !fi.IsDir() {
-				base.Errorf("go get: %s exists as a file, but 'go get' requires package arguments", q.raw)
+				base.Errorf("go: %s exists as a file, but 'go get' requires package arguments", q.raw)
 				continue
 			}
 		}
@@ -743,7 +743,7 @@
 
 			if len(match.Pkgs) == 0 {
 				if q.raw == "" || q.raw == "." {
-					return errSet(fmt.Errorf("no package in current directory"))
+					return errSet(fmt.Errorf("no package to get in current directory"))
 				}
 				if !q.isWildcard() {
 					modload.MustHaveModRoot()
@@ -1342,7 +1342,7 @@
 	var tentative []module.Version
 	for _, cs := range upgrades {
 		if cs.err != nil {
-			base.Errorf("go get: %v", cs.err)
+			base.Errorf("go: %v", cs.err)
 			continue
 		}
 
@@ -1735,13 +1735,13 @@
 	})
 	for _, c := range sortedChanges {
 		if c.old == "" {
-			fmt.Fprintf(os.Stderr, "go get: added %s %s\n", c.path, c.new)
+			fmt.Fprintf(os.Stderr, "go: added %s %s\n", c.path, c.new)
 		} else if c.new == "none" || c.new == "" {
-			fmt.Fprintf(os.Stderr, "go get: removed %s %s\n", c.path, c.old)
+			fmt.Fprintf(os.Stderr, "go: removed %s %s\n", c.path, c.old)
 		} else if semver.Compare(c.new, c.old) > 0 {
-			fmt.Fprintf(os.Stderr, "go get: upgraded %s %s => %s\n", c.path, c.old, c.new)
+			fmt.Fprintf(os.Stderr, "go: upgraded %s %s => %s\n", c.path, c.old, c.new)
 		} else {
-			fmt.Fprintf(os.Stderr, "go get: downgraded %s %s => %s\n", c.path, c.old, c.new)
+			fmt.Fprintf(os.Stderr, "go: downgraded %s %s => %s\n", c.path, c.old, c.new)
 		}
 	}
 
@@ -1800,7 +1800,7 @@
 	if err != nil {
 		var constraint *modload.ConstraintError
 		if !errors.As(err, &constraint) {
-			base.Errorf("go get: %v", err)
+			base.Errorf("go: %v", err)
 			return false
 		}
 
@@ -1812,7 +1812,7 @@
 			return rv.reason.ResolvedString(module.Version{Path: m.Path, Version: rv.version})
 		}
 		for _, c := range constraint.Conflicts {
-			base.Errorf("go get: %v requires %v, not %v", reason(c.Source), c.Dep, reason(c.Constraint))
+			base.Errorf("go: %v requires %v, not %v", reason(c.Source), c.Dep, reason(c.Constraint))
 		}
 		return false
 	}
diff --git a/src/cmd/go/internal/modget/query.go b/src/cmd/go/internal/modget/query.go
index 7604190..d7341e7 100644
--- a/src/cmd/go/internal/modget/query.go
+++ b/src/cmd/go/internal/modget/query.go
@@ -284,21 +284,21 @@
 	patternRE := regexp.MustCompile("(?m)(?:[ \t(\"`]|^)" + regexp.QuoteMeta(q.pattern) + "(?:[ @:;)\"`]|$)")
 	if patternRE.MatchString(errStr) {
 		if q.rawVersion == "" {
-			base.Errorf("go get: %s", errStr)
+			base.Errorf("go: %s", errStr)
 			return
 		}
 
 		versionRE := regexp.MustCompile("(?m)(?:[ @(\"`]|^)" + regexp.QuoteMeta(q.version) + "(?:[ :;)\"`]|$)")
 		if versionRE.MatchString(errStr) {
-			base.Errorf("go get: %s", errStr)
+			base.Errorf("go: %s", errStr)
 			return
 		}
 	}
 
 	if qs := q.String(); qs != "" {
-		base.Errorf("go get %s: %s", qs, errStr)
+		base.Errorf("go: %s: %s", qs, errStr)
 	} else {
-		base.Errorf("go get: %s", errStr)
+		base.Errorf("go: %s", errStr)
 	}
 }
 
diff --git a/src/cmd/go/internal/modload/load.go b/src/cmd/go/internal/modload/load.go
index 20c007a..40e6b50 100644
--- a/src/cmd/go/internal/modload/load.go
+++ b/src/cmd/go/internal/modload/load.go
@@ -970,7 +970,7 @@
 		ld.GoVersion = MainModules.GoVersion()
 
 		if ld.Tidy && semver.Compare("v"+ld.GoVersion, "v"+LatestGoVersion()) > 0 {
-			ld.errorf("go mod tidy: go.mod file indicates go %s, but maximum supported version is %s\n", ld.GoVersion, LatestGoVersion())
+			ld.errorf("go: go.mod file indicates go %s, but maximum version supported by tidy is %s\n", ld.GoVersion, LatestGoVersion())
 			base.ExitIfErrors()
 		}
 	}
@@ -1142,7 +1142,7 @@
 			// If that is not the case, there is a bug in the loading loop above.
 			for _, m := range rs.rootModules {
 				if v, ok := ld.requirements.rootSelected(m.Path); !ok || v != m.Version {
-					ld.errorf("go mod tidy: internal error: a requirement on %v is needed but was not added during package loading\n", m)
+					ld.errorf("go: internal error: a requirement on %v is needed but was not added during package loading\n", m)
 					base.ExitIfErrors()
 				}
 			}
@@ -1884,7 +1884,7 @@
 
 	mg, err := rs.Graph(ctx)
 	if err != nil {
-		ld.errorf("go mod tidy: error loading go %s module graph: %v\n", ld.TidyCompatibleVersion, err)
+		ld.errorf("go: error loading go %s module graph: %v\n", ld.TidyCompatibleVersion, err)
 		suggestFixes()
 		return
 	}
diff --git a/src/cmd/go/internal/run/run.go b/src/cmd/go/internal/run/run.go
index 931fdce..11e2c81 100644
--- a/src/cmd/go/internal/run/run.go
+++ b/src/cmd/go/internal/run/run.go
@@ -103,7 +103,7 @@
 			if strings.HasSuffix(file, "_test.go") {
 				// GoFilesPackage is going to assign this to TestGoFiles.
 				// Reject since it won't be part of the build.
-				base.Fatalf("go run: cannot run *_test.go files (%s)", file)
+				base.Fatalf("go: cannot run *_test.go files (%s)", file)
 			}
 		}
 		p = load.GoFilesPackage(ctx, pkgOpts, files)
@@ -114,26 +114,26 @@
 			var err error
 			pkgs, err = load.PackagesAndErrorsOutsideModule(ctx, pkgOpts, args[:1])
 			if err != nil {
-				base.Fatalf("go run: %v", err)
+				base.Fatalf("go: %v", err)
 			}
 		} else {
 			pkgs = load.PackagesAndErrors(ctx, pkgOpts, args[:1])
 		}
 
 		if len(pkgs) == 0 {
-			base.Fatalf("go run: no packages loaded from %s", arg)
+			base.Fatalf("go: no packages loaded from %s", arg)
 		}
 		if len(pkgs) > 1 {
 			var names []string
 			for _, p := range pkgs {
 				names = append(names, p.ImportPath)
 			}
-			base.Fatalf("go run: pattern %s matches multiple packages:\n\t%s", arg, strings.Join(names, "\n\t"))
+			base.Fatalf("go: pattern %s matches multiple packages:\n\t%s", arg, strings.Join(names, "\n\t"))
 		}
 		p = pkgs[0]
 		i++
 	} else {
-		base.Fatalf("go run: no go files listed")
+		base.Fatalf("go: no go files listed")
 	}
 	cmdArgs := args[i:]
 	load.CheckPackageErrors([]*load.Package{p})
@@ -154,7 +154,7 @@
 			if !cfg.BuildContext.CgoEnabled {
 				hint = " (cgo is disabled)"
 			}
-			base.Fatalf("go run: no suitable source files%s", hint)
+			base.Fatalf("go: no suitable source files%s", hint)
 		}
 		p.Internal.ExeName = src[:len(src)-len(".go")]
 	} else {
diff --git a/src/cmd/go/internal/test/test.go b/src/cmd/go/internal/test/test.go
index d65f54f..198afbf 100644
--- a/src/cmd/go/internal/test/test.go
+++ b/src/cmd/go/internal/test/test.go
@@ -656,7 +656,7 @@
 	b.Init()
 
 	if cfg.BuildI {
-		fmt.Fprint(os.Stderr, "go test: -i flag is deprecated\n")
+		fmt.Fprint(os.Stderr, "go: -i flag is deprecated\n")
 		cfg.BuildV = testV
 
 		deps := make(map[string]bool)
diff --git a/src/cmd/go/internal/test/testflag.go b/src/cmd/go/internal/test/testflag.go
index 97a9ef3..e0a3e01 100644
--- a/src/cmd/go/internal/test/testflag.go
+++ b/src/cmd/go/internal/test/testflag.go
@@ -384,7 +384,7 @@
 		if !testC {
 			buildFlag = "-i"
 		}
-		fmt.Fprintf(os.Stderr, "go test: unknown flag %s cannot be used with %s\n", firstUnknownFlag, buildFlag)
+		fmt.Fprintf(os.Stderr, "go: unknown flag %s cannot be used with %s\n", firstUnknownFlag, buildFlag)
 		exitWithUsage()
 	}
 
diff --git a/src/cmd/go/internal/tool/tool.go b/src/cmd/go/internal/tool/tool.go
index 95c90ea..4fe4c2b 100644
--- a/src/cmd/go/internal/tool/tool.go
+++ b/src/cmd/go/internal/tool/tool.go
@@ -61,7 +61,7 @@
 		switch {
 		case 'a' <= c && c <= 'z', '0' <= c && c <= '9', c == '_':
 		default:
-			fmt.Fprintf(os.Stderr, "go tool: bad tool name %q\n", toolName)
+			fmt.Fprintf(os.Stderr, "go: bad tool name %q\n", toolName)
 			base.SetExitStatus(2)
 			return
 		}
@@ -117,14 +117,14 @@
 func listTools() {
 	f, err := os.Open(base.ToolDir)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "go tool: no tool directory: %s\n", err)
+		fmt.Fprintf(os.Stderr, "go: no tool directory: %s\n", err)
 		base.SetExitStatus(2)
 		return
 	}
 	defer f.Close()
 	names, err := f.Readdirnames(-1)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "go tool: can't read directory: %s\n", err)
+		fmt.Fprintf(os.Stderr, "go: can't read tool directory: %s\n", err)
 		base.SetExitStatus(2)
 		return
 	}
diff --git a/src/cmd/go/internal/version/version.go b/src/cmd/go/internal/version/version.go
index 58cbd32..e885933 100644
--- a/src/cmd/go/internal/version/version.go
+++ b/src/cmd/go/internal/version/version.go
@@ -62,8 +62,14 @@
 		// a reasonable use case. For example, imagine GOFLAGS=-v to
 		// turn "verbose mode" on for all Go commands, which should not
 		// break "go version".
-		if (!base.InGOFLAGS("-m") && *versionM) || (!base.InGOFLAGS("-v") && *versionV) {
-			fmt.Fprintf(os.Stderr, "go version: flags can only be used with arguments\n")
+		var argOnlyFlag string
+		if !base.InGOFLAGS("-m") && *versionM {
+			argOnlyFlag = "-m"
+		} else if !base.InGOFLAGS("-v") && *versionV {
+			argOnlyFlag = "-v"
+		}
+		if argOnlyFlag != "" {
+			fmt.Fprintf(os.Stderr, "go: 'go version' only accepts %s flag with arguments\n", argOnlyFlag)
 			base.SetExitStatus(2)
 			return
 		}
diff --git a/src/cmd/go/internal/vet/vet.go b/src/cmd/go/internal/vet/vet.go
index 1d419dd..88b3c57 100644
--- a/src/cmd/go/internal/vet/vet.go
+++ b/src/cmd/go/internal/vet/vet.go
@@ -103,7 +103,7 @@
 			continue
 		}
 		if len(ptest.GoFiles) == 0 && len(ptest.CgoFiles) == 0 && pxtest == nil {
-			base.Errorf("go vet %s: no Go files in %s", p.ImportPath, p.Dir)
+			base.Errorf("go: can't vet %s: no Go files in %s", p.ImportPath, p.Dir)
 			continue
 		}
 		if len(ptest.GoFiles) > 0 || len(ptest.CgoFiles) > 0 {
diff --git a/src/cmd/go/internal/vet/vetflag.go b/src/cmd/go/internal/vet/vetflag.go
index b5b3c46..3551a59 100644
--- a/src/cmd/go/internal/vet/vetflag.go
+++ b/src/cmd/go/internal/vet/vetflag.go
@@ -82,7 +82,7 @@
 	vetcmd := exec.Command(tool, "-flags")
 	vetcmd.Stdout = out
 	if err := vetcmd.Run(); err != nil {
-		fmt.Fprintf(os.Stderr, "go vet: can't execute %s -flags: %v\n", tool, err)
+		fmt.Fprintf(os.Stderr, "go: can't execute %s -flags: %v\n", tool, err)
 		base.SetExitStatus(2)
 		base.Exit()
 	}
@@ -92,7 +92,7 @@
 		Usage string
 	}
 	if err := json.Unmarshal(out.Bytes(), &analysisFlags); err != nil {
-		fmt.Fprintf(os.Stderr, "go vet: can't unmarshal JSON from %s -flags: %v", tool, err)
+		fmt.Fprintf(os.Stderr, "go: can't unmarshal JSON from %s -flags: %v", tool, err)
 		base.SetExitStatus(2)
 		base.Exit()
 	}
diff --git a/src/cmd/go/internal/work/action.go b/src/cmd/go/internal/work/action.go
index 69940cb..6f5ac13 100644
--- a/src/cmd/go/internal/work/action.go
+++ b/src/cmd/go/internal/work/action.go
@@ -294,14 +294,14 @@
 	}
 
 	if err := CheckGOOSARCHPair(cfg.Goos, cfg.Goarch); err != nil {
-		fmt.Fprintf(os.Stderr, "cmd/go: %v\n", err)
+		fmt.Fprintf(os.Stderr, "go: %v\n", err)
 		base.SetExitStatus(2)
 		base.Exit()
 	}
 
 	for _, tag := range cfg.BuildContext.BuildTags {
 		if strings.Contains(tag, ",") {
-			fmt.Fprintf(os.Stderr, "cmd/go: -tags space-separated list contains comma\n")
+			fmt.Fprintf(os.Stderr, "go: -tags space-separated list contains comma\n")
 			base.SetExitStatus(2)
 			base.Exit()
 		}
diff --git a/src/cmd/go/internal/work/build.go b/src/cmd/go/internal/work/build.go
index 3d7c778..e5d7f4a 100644
--- a/src/cmd/go/internal/work/build.go
+++ b/src/cmd/go/internal/work/build.go
@@ -406,7 +406,7 @@
 	depMode := ModeBuild
 	if cfg.BuildI {
 		depMode = ModeInstall
-		fmt.Fprint(os.Stderr, "go build: -i flag is deprecated\n")
+		fmt.Fprint(os.Stderr, "go: -i flag is deprecated\n")
 	}
 
 	pkgs = omitTestOnly(pkgsFilter(pkgs))
@@ -425,7 +425,7 @@
 			strings.HasSuffix(cfg.BuildO, "/") ||
 			strings.HasSuffix(cfg.BuildO, string(os.PathSeparator)) {
 			if !explicitO {
-				base.Fatalf("go build: build output %q already exists and is a directory", cfg.BuildO)
+				base.Fatalf("go: build output %q already exists and is a directory", cfg.BuildO)
 			}
 			a := &Action{Mode: "go build"}
 			for _, p := range pkgs {
@@ -440,13 +440,13 @@
 				a.Deps = append(a.Deps, b.AutoAction(ModeInstall, depMode, p))
 			}
 			if len(a.Deps) == 0 {
-				base.Fatalf("go build: no main packages to build")
+				base.Fatalf("go: no main packages to build")
 			}
 			b.Do(ctx, a)
 			return
 		}
 		if len(pkgs) > 1 {
-			base.Fatalf("go build: cannot write multiple packages to non-directory %s", cfg.BuildO)
+			base.Fatalf("go: cannot write multiple packages to non-directory %s", cfg.BuildO)
 		} else if len(pkgs) == 0 {
 			base.Fatalf("no packages to build")
 		}
@@ -593,7 +593,7 @@
 	for _, arg := range args {
 		if strings.Contains(arg, "@") && !build.IsLocalImport(arg) && !filepath.IsAbs(arg) {
 			if cfg.BuildI {
-				fmt.Fprint(os.Stderr, "go install: -i flag is deprecated\n")
+				fmt.Fprint(os.Stderr, "go: -i flag is deprecated\n")
 			}
 			installOutsideModule(ctx, args)
 			return
@@ -621,7 +621,7 @@
 				latestArgs[i] = args[i] + "@latest"
 			}
 			hint := strings.Join(latestArgs, " ")
-			base.Fatalf("go install: version is required when current directory is not in a module\n\tTry 'go install %s' to install the latest version", hint)
+			base.Fatalf("go: 'go install' requires a version when current directory is not in a module\n\tTry 'go install %s' to install the latest version", hint)
 		}
 	}
 	load.CheckPackageErrors(pkgs)
@@ -634,7 +634,7 @@
 			}
 		}
 		if !allGoroot {
-			fmt.Fprint(os.Stderr, "go install: -i flag is deprecated\n")
+			fmt.Fprintf(os.Stderr, "go: -i flag is deprecated\n")
 		}
 	}
 
@@ -680,14 +680,14 @@
 			case p.Name != "main" && p.Module != nil:
 				// Non-executables have no target (except the cache) when building with modules.
 			case p.Internal.GobinSubdir:
-				base.Errorf("go %s: cannot install cross-compiled binaries when GOBIN is set", cfg.CmdName)
+				base.Errorf("go: cannot install cross-compiled binaries when GOBIN is set")
 			case p.Internal.CmdlineFiles:
-				base.Errorf("go %s: no install location for .go files listed on command line (GOBIN not set)", cfg.CmdName)
+				base.Errorf("go: no install location for .go files listed on command line (GOBIN not set)")
 			case p.ConflictDir != "":
-				base.Errorf("go %s: no install location for %s: hidden by %s", cfg.CmdName, p.Dir, p.ConflictDir)
+				base.Errorf("go: no install location for %s: hidden by %s", p.Dir, p.ConflictDir)
 			default:
-				base.Errorf("go %s: no install location for directory %s outside GOPATH\n"+
-					"\tFor more details see: 'go help gopath'", cfg.CmdName, p.Dir)
+				base.Errorf("go: no install location for directory %s outside GOPATH\n"+
+					"\tFor more details see: 'go help gopath'", p.Dir)
 			}
 		}
 	}
@@ -782,7 +782,7 @@
 	pkgOpts := load.PackageOpts{MainOnly: true}
 	pkgs, err := load.PackagesAndErrorsOutsideModule(ctx, pkgOpts, args)
 	if err != nil {
-		base.Fatalf("go install: %v", err)
+		base.Fatalf("go: %v", err)
 	}
 	load.CheckPackageErrors(pkgs)
 	patterns := make([]string, len(args))
diff --git a/src/cmd/go/internal/work/init.go b/src/cmd/go/internal/work/init.go
index 7acee3d..7aa8dfe 100644
--- a/src/cmd/go/internal/work/init.go
+++ b/src/cmd/go/internal/work/init.go
@@ -13,7 +13,6 @@
 	"cmd/go/internal/modload"
 	"cmd/internal/str"
 	"cmd/internal/sys"
-	"flag"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -33,7 +32,7 @@
 	if cfg.BuildPkgdir != "" && !filepath.IsAbs(cfg.BuildPkgdir) {
 		p, err := filepath.Abs(cfg.BuildPkgdir)
 		if err != nil {
-			fmt.Fprintf(os.Stderr, "go %s: evaluating -pkgdir: %v\n", flag.Args()[0], err)
+			fmt.Fprintf(os.Stderr, "go: evaluating -pkgdir: %v\n", err)
 			base.SetExitStatus(2)
 			base.Exit()
 		}
@@ -49,14 +48,14 @@
 		value := cfg.Getenv(key)
 		args, err := str.SplitQuotedFields(value)
 		if err != nil {
-			base.Fatalf("go %s: %s environment variable could not be parsed: %v", flag.Args()[0], key, err)
+			base.Fatalf("go: %s environment variable could not be parsed: %v", key, err)
 		}
 		if len(args) == 0 {
 			continue
 		}
 		path := args[0]
 		if !filepath.IsAbs(path) && path != filepath.Base(path) {
-			base.Fatalf("go %s: %s environment variable is relative; must be absolute path: %s\n", flag.Args()[0], key, path)
+			base.Fatalf("go: %s environment variable is relative; must be absolute path: %s\n", key, path)
 		}
 	}
 }
@@ -66,7 +65,7 @@
 		return
 	}
 	if cfg.BuildRace && cfg.BuildMSan {
-		fmt.Fprintf(os.Stderr, "go %s: may not use -race and -msan simultaneously\n", flag.Args()[0])
+		fmt.Fprintf(os.Stderr, "go: may not use -race and -msan simultaneously\n")
 		base.SetExitStatus(2)
 		base.Exit()
 	}
@@ -77,7 +76,7 @@
 	}
 	if cfg.BuildRace {
 		if !sys.RaceDetectorSupported(cfg.Goos, cfg.Goarch) {
-			fmt.Fprintf(os.Stderr, "go %s: -race is only supported on linux/amd64, linux/ppc64le, linux/arm64, freebsd/amd64, netbsd/amd64, darwin/amd64, darwin/arm64, and windows/amd64\n", flag.Args()[0])
+			fmt.Fprintf(os.Stderr, "go: -race is only supported on linux/amd64, linux/ppc64le, linux/arm64, freebsd/amd64, netbsd/amd64, darwin/amd64, darwin/arm64, and windows/amd64\n")
 			base.SetExitStatus(2)
 			base.Exit()
 		}
@@ -95,9 +94,9 @@
 
 	if !cfg.BuildContext.CgoEnabled {
 		if runtime.GOOS != cfg.Goos || runtime.GOARCH != cfg.Goarch {
-			fmt.Fprintf(os.Stderr, "go %s: %s requires cgo\n", flag.Args()[0], modeFlag)
+			fmt.Fprintf(os.Stderr, "go: %s requires cgo\n", modeFlag)
 		} else {
-			fmt.Fprintf(os.Stderr, "go %s: %s requires cgo; enable cgo by setting CGO_ENABLED=1\n", flag.Args()[0], modeFlag)
+			fmt.Fprintf(os.Stderr, "go: %s requires cgo; enable cgo by setting CGO_ENABLED=1\n", modeFlag)
 		}
 
 		base.SetExitStatus(2)
diff --git a/src/cmd/go/testdata/script/build_i_deprecate.txt b/src/cmd/go/testdata/script/build_i_deprecate.txt
index 71356e5..5c17995 100644
--- a/src/cmd/go/testdata/script/build_i_deprecate.txt
+++ b/src/cmd/go/testdata/script/build_i_deprecate.txt
@@ -2,13 +2,13 @@
 # TODO(golang.org/issue/41696): remove the -i flag after Go 1.16, and this test.
 
 go build -n -i
-stderr '^go build: -i flag is deprecated$'
+stderr '^go: -i flag is deprecated$'
 
 go install -n -i
-stderr '^go install: -i flag is deprecated$'
+stderr '^go: -i flag is deprecated$'
 
 go test -n -i
-stderr '^go test: -i flag is deprecated$'
+stderr '^go: -i flag is deprecated$'
 
 
 # 'go clean -i' should not print a deprecation warning.
diff --git a/src/cmd/go/testdata/script/env_unset.txt b/src/cmd/go/testdata/script/env_unset.txt
index 4e0f249..22bc845 100644
--- a/src/cmd/go/testdata/script/env_unset.txt
+++ b/src/cmd/go/testdata/script/env_unset.txt
@@ -12,13 +12,13 @@
 go env -u GOEXPERIMENT
 
 ! go env
-stderr '^cmd/go: unsupported GOOS/GOARCH pair bados/badarch$'
+stderr '^go: unsupported GOOS/GOARCH pair bados/badarch$'
 
 ! go env -u GOOS
-stderr '^go env -u: unsupported GOOS/GOARCH pair \w+/badarch$'
+stderr '^go: unsupported GOOS/GOARCH pair \w+/badarch$'
 
 ! go env -u GOARCH
-stderr '^go env -u: unsupported GOOS/GOARCH pair bados/\w+$'
+stderr '^go: unsupported GOOS/GOARCH pair bados/\w+$'
 
 go env -u GOOS GOARCH
 
diff --git a/src/cmd/go/testdata/script/env_write.txt b/src/cmd/go/testdata/script/env_write.txt
index b5e9739..132947c 100644
--- a/src/cmd/go/testdata/script/env_write.txt
+++ b/src/cmd/go/testdata/script/env_write.txt
@@ -30,9 +30,9 @@
 
 # checking errors
 ! go env -w
-stderr 'go env -w: no KEY=VALUE arguments given'
+stderr 'go: no KEY=VALUE arguments given'
 ! go env -u
-stderr 'go env -u: no arguments given'
+stderr 'go: ''go env -u'' requires an argument'
 
 # go env -w changes default setting
 env root=
@@ -111,7 +111,7 @@
 
 # go env -w rejects invalid GOTMPDIR values
 ! go env -w GOTMPDIR=x
-stderr 'go env -w: GOTMPDIR must be an absolute path'
+stderr 'go: GOTMPDIR must be an absolute path'
 
 # go env -w should accept absolute GOTMPDIR value
 # and should not create it
@@ -134,24 +134,24 @@
 go env -w CC=clang
 [!windows] ! go env -w CC=./clang
 [!windows] ! go env -w CC=bin/clang
-[!windows] stderr 'go env -w: CC entry is relative; must be absolute path'
+[!windows] stderr 'go: CC entry is relative; must be absolute path'
 
 [windows] go env -w CC=$WORK\bin\clang
 [windows] ! go env -w CC=.\clang
 [windows] ! go env -w CC=bin\clang
-[windows] stderr 'go env -w: CC entry is relative; must be absolute path'
+[windows] stderr 'go: CC entry is relative; must be absolute path'
 
 # go env -w rejects relative CXX values
 [!windows] go env -w CC=/usr/bin/cpp
 go env -w CXX=cpp
 [!windows] ! go env -w CXX=./cpp
 [!windows] ! go env -w CXX=bin/cpp
-[!windows] stderr 'go env -w: CXX entry is relative; must be absolute path'
+[!windows] stderr 'go: CXX entry is relative; must be absolute path'
 
 [windows] go env -w CXX=$WORK\bin\cpp
 [windows] ! go env -w CXX=.\cpp
 [windows] ! go env -w CXX=bin\cpp
-[windows] stderr 'go env -w: CXX entry is relative; must be absolute path'
+[windows] stderr 'go: CXX entry is relative; must be absolute path'
 
 # go env -w/-u checks validity of GOOS/ARCH combinations
 env GOOS=
@@ -176,9 +176,9 @@
 
 # go env -w should reject relative paths in GOMODCACHE environment.
 ! go env -w GOMODCACHE=~/test
-stderr 'go env -w: GOMODCACHE entry is relative; must be absolute path: "~/test"'
+stderr 'go: GOMODCACHE entry is relative; must be absolute path: "~/test"'
 ! go env -w GOMODCACHE=./test
-stderr 'go env -w: GOMODCACHE entry is relative; must be absolute path: "./test"'
+stderr 'go: GOMODCACHE entry is relative; must be absolute path: "./test"'
 
 # go env -w checks validity of GOEXPERIMENT
 env GOEXPERIMENT=
diff --git a/src/cmd/go/testdata/script/get_go_file.txt b/src/cmd/go/testdata/script/get_go_file.txt
index bed8720..f6d0de4 100644
--- a/src/cmd/go/testdata/script/get_go_file.txt
+++ b/src/cmd/go/testdata/script/get_go_file.txt
@@ -9,15 +9,15 @@
 
 # argument has .go suffix, is a file and exists
 ! go get -d test.go
-stderr 'go get test.go: arguments must be package or module paths'
+stderr 'go: test.go: arguments must be package or module paths'
 
 # argument has .go suffix, doesn't exist and has no slashes
 ! go get -d test_missing.go
-stderr 'go get test_missing.go: arguments must be package or module paths'
+stderr 'go: test_missing.go: arguments must be package or module paths'
 
 # argument has .go suffix, is a file and exists in sub-directory
 ! go get -d test/test.go
-stderr 'go get: test/test.go exists as a file, but ''go get'' requires package arguments'
+stderr 'go: test/test.go exists as a file, but ''go get'' requires package arguments'
 
 # argument has .go suffix, doesn't exist and has slashes
 ! go get -d test/test_missing.go
@@ -27,19 +27,19 @@
 # argument has .go suffix, is a symlink and exists
 [symlink] symlink test_sym.go -> test.go
 [symlink] ! go get -d test_sym.go
-[symlink] stderr 'go get test_sym.go: arguments must be package or module paths'
+[symlink] stderr 'go: test_sym.go: arguments must be package or module paths'
 [symlink] rm test_sym.go
 
 # argument has .go suffix, is a symlink and exists in sub-directory
 [symlink] symlink test/test_sym.go -> test.go
 [symlink] ! go get -d test/test_sym.go
-[symlink] stderr 'go get: test/test_sym.go exists as a file, but ''go get'' requires package arguments'
+[symlink] stderr 'go: test/test_sym.go exists as a file, but ''go get'' requires package arguments'
 [symlink] rm test_sym.go
 
 # argument has .go suffix, is a directory and exists
 mkdir test_dir.go
 ! go get -d test_dir.go
-stderr 'go get test_dir.go: arguments must be package or module paths'
+stderr 'go: test_dir.go: arguments must be package or module paths'
 rm test_dir.go
 
 # argument has .go suffix, is a directory and exists in sub-directory
diff --git a/src/cmd/go/testdata/script/get_insecure_no_longer_supported.txt b/src/cmd/go/testdata/script/get_insecure_no_longer_supported.txt
index 2517664..00bf32f 100644
--- a/src/cmd/go/testdata/script/get_insecure_no_longer_supported.txt
+++ b/src/cmd/go/testdata/script/get_insecure_no_longer_supported.txt
@@ -3,11 +3,11 @@
 
 # GOPATH: Fetch with insecure, should error
 ! go get -insecure test
-stderr 'go get: -insecure flag is no longer supported; use GOINSECURE instead'
+stderr 'go: -insecure flag is no longer supported; use GOINSECURE instead'
 
 # Modules: Set up
 env GO111MODULE=on
 
 # Modules: Fetch with insecure, should error
 ! go get -insecure test
-stderr 'go get: -insecure flag is no longer supported; use GOINSECURE instead'
+stderr 'go: -insecure flag is no longer supported; use GOINSECURE instead'
diff --git a/src/cmd/go/testdata/script/gopath_install.txt b/src/cmd/go/testdata/script/gopath_install.txt
index 4b42fc5..6c572ea 100644
--- a/src/cmd/go/testdata/script/gopath_install.txt
+++ b/src/cmd/go/testdata/script/gopath_install.txt
@@ -26,7 +26,7 @@
 env GOPATH= # reset to default ($HOME/go, which does not exist)
 env GOBIN=
 ! go install go-cmd-test/helloworld.go
-stderr '^go install: no install location for \.go files listed on command line \(GOBIN not set\)$'
+stderr '^go: no install location for \.go files listed on command line \(GOBIN not set\)$'
 
 # With $GOBIN set, should install there.
 env GOBIN=$WORK/bin1
diff --git a/src/cmd/go/testdata/script/gopath_local.txt b/src/cmd/go/testdata/script/gopath_local.txt
index 7ee1f83..54beaca 100644
--- a/src/cmd/go/testdata/script/gopath_local.txt
+++ b/src/cmd/go/testdata/script/gopath_local.txt
@@ -22,7 +22,7 @@
 # Explicit source files listed on the command line should not install without
 # GOBIN set, since individual source files aren't part of the containing GOPATH.
 ! go install testdata/local/easy.go
-stderr '^go install: no install location for \.go files listed on command line \(GOBIN not set\)$'
+stderr '^go: no install location for \.go files listed on command line \(GOBIN not set\)$'
 
 [windows] stop  # Windows does not allow the ridiculous directory name we're about to use.
 
@@ -58,7 +58,7 @@
 # Explicit source files listed on the command line should not install without
 # GOBIN set, since individual source files aren't part of the containing GOPATH.
 ! go install testdata/$BAD_DIR_NAME/easy.go
-stderr '^go install: no install location for \.go files listed on command line \(GOBIN not set\)$'
+stderr '^go: no install location for \.go files listed on command line \(GOBIN not set\)$'
 
 -- testdata/local/easy.go --
 package main
diff --git a/src/cmd/go/testdata/script/govcs.txt b/src/cmd/go/testdata/script/govcs.txt
index 4180d7d..e8dd791 100644
--- a/src/cmd/go/testdata/script/govcs.txt
+++ b/src/cmd/go/testdata/script/govcs.txt
@@ -5,40 +5,40 @@
 # GOVCS stops go get
 env GOVCS='*:none'
 ! go get github.com/google/go-cmp
-stderr '^go get: GOVCS disallows using git for public github.com/google/go-cmp; see ''go help vcs''$'
+stderr '^go: GOVCS disallows using git for public github.com/google/go-cmp; see ''go help vcs''$'
 env GOPRIVATE='github.com/google'
 ! go get github.com/google/go-cmp
-stderr '^go get: GOVCS disallows using git for private github.com/google/go-cmp; see ''go help vcs''$'
+stderr '^go: GOVCS disallows using git for private github.com/google/go-cmp; see ''go help vcs''$'
 
 # public pattern works
 env GOPRIVATE='github.com/google'
 env GOVCS='public:all,private:none'
 ! go get github.com/google/go-cmp
-stderr '^go get: GOVCS disallows using git for private github.com/google/go-cmp; see ''go help vcs''$'
+stderr '^go: GOVCS disallows using git for private github.com/google/go-cmp; see ''go help vcs''$'
 
 # private pattern works
 env GOPRIVATE='hubgit.com/google'
 env GOVCS='private:all,public:none'
 ! go get github.com/google/go-cmp
-stderr '^go get: GOVCS disallows using git for public github.com/google/go-cmp; see ''go help vcs''$'
+stderr '^go: GOVCS disallows using git for public github.com/google/go-cmp; see ''go help vcs''$'
 
 # other patterns work (for more patterns, see TestGOVCS)
 env GOPRIVATE=
 env GOVCS='github.com:svn|hg'
 ! go get github.com/google/go-cmp
-stderr '^go get: GOVCS disallows using git for public github.com/google/go-cmp; see ''go help vcs''$'
+stderr '^go: GOVCS disallows using git for public github.com/google/go-cmp; see ''go help vcs''$'
 env GOVCS='github.com/google/go-cmp/inner:git,github.com:svn|hg'
 ! go get github.com/google/go-cmp
-stderr '^go get: GOVCS disallows using git for public github.com/google/go-cmp; see ''go help vcs''$'
+stderr '^go: GOVCS disallows using git for public github.com/google/go-cmp; see ''go help vcs''$'
 
 # bad patterns are reported (for more bad patterns, see TestGOVCSErrors)
 env GOVCS='git'
 ! go get github.com/google/go-cmp
-stderr '^go get github.com/google/go-cmp: malformed entry in GOVCS \(missing colon\): "git"$'
+stderr '^go: github.com/google/go-cmp: malformed entry in GOVCS \(missing colon\): "git"$'
 
 env GOVCS=github.com:hg,github.com:git
 ! go get github.com/google/go-cmp
-stderr '^go get github.com/google/go-cmp: unreachable pattern in GOVCS: "github.com:git" after "github.com:hg"$'
+stderr '^go: github.com/google/go-cmp: unreachable pattern in GOVCS: "github.com:git" after "github.com:hg"$'
 
 # bad GOVCS patterns do not stop commands that do not need to check VCS
 go list
@@ -50,19 +50,19 @@
 env GOPRIVATE=
 env GOVCS=
 ! go get rsc.io/nonexist.svn/hello
-stderr '^go get rsc.io/nonexist.svn/hello: GOVCS disallows using svn for public rsc.io/nonexist.svn; see ''go help vcs''$'
+stderr '^go: rsc.io/nonexist.svn/hello: GOVCS disallows using svn for public rsc.io/nonexist.svn; see ''go help vcs''$'
 
 # fossil is disallowed by default
 env GOPRIVATE=
 env GOVCS=
 ! go get rsc.io/nonexist.fossil/hello
-stderr '^go get rsc.io/nonexist.fossil/hello: GOVCS disallows using fossil for public rsc.io/nonexist.fossil; see ''go help vcs''$'
+stderr '^go: rsc.io/nonexist.fossil/hello: GOVCS disallows using fossil for public rsc.io/nonexist.fossil; see ''go help vcs''$'
 
 # bzr is disallowed by default
 env GOPRIVATE=
 env GOVCS=
 ! go get rsc.io/nonexist.bzr/hello
-stderr '^go get rsc.io/nonexist.bzr/hello: GOVCS disallows using bzr for public rsc.io/nonexist.bzr; see ''go help vcs''$'
+stderr '^go: rsc.io/nonexist.bzr/hello: GOVCS disallows using bzr for public rsc.io/nonexist.bzr; see ''go help vcs''$'
 
 # git is OK by default
 env GOVCS=
@@ -77,12 +77,12 @@
 # git can be disallowed
 env GOVCS=public:hg
 ! go get rsc.io/nonexist.git/hello
-stderr '^go get rsc.io/nonexist.git/hello: GOVCS disallows using git for public rsc.io/nonexist.git; see ''go help vcs''$'
+stderr '^go: rsc.io/nonexist.git/hello: GOVCS disallows using git for public rsc.io/nonexist.git; see ''go help vcs''$'
 
 # hg can be disallowed
 env GOVCS=public:git
 ! go get rsc.io/nonexist.hg/hello
-stderr '^go get rsc.io/nonexist.hg/hello: GOVCS disallows using hg for public rsc.io/nonexist.hg; see ''go help vcs''$'
+stderr '^go: rsc.io/nonexist.hg/hello: GOVCS disallows using hg for public rsc.io/nonexist.hg; see ''go help vcs''$'
 
 # Repeat in GOPATH mode. Error texts slightly different.
 
diff --git a/src/cmd/go/testdata/script/list_shadow.txt b/src/cmd/go/testdata/script/list_shadow.txt
index 7b24d93..660508d 100644
--- a/src/cmd/go/testdata/script/list_shadow.txt
+++ b/src/cmd/go/testdata/script/list_shadow.txt
@@ -15,7 +15,7 @@
 
 # The error for go install should mention the conflicting directory.
 ! go install -n ./shadow/root2/src/foo
-stderr 'go install: no install location for '$WORK'(\\|/)?gopath(\\|/)src(\\|/)shadow(\\|/)root2(\\|/)src(\\|/)foo: hidden by '$WORK'(\\|/)?gopath(\\|/)src(\\|/)shadow(\\|/)root1(\\|/)src(\\|/)foo'
+stderr 'go: no install location for '$WORK'(\\|/)?gopath(\\|/)src(\\|/)shadow(\\|/)root2(\\|/)src(\\|/)foo: hidden by '$WORK'(\\|/)?gopath(\\|/)src(\\|/)shadow(\\|/)root1(\\|/)src(\\|/)foo'
 
 -- shadow/root1/src/foo/foo.go --
 package foo
diff --git a/src/cmd/go/testdata/script/mod_bad_domain.txt b/src/cmd/go/testdata/script/mod_bad_domain.txt
index 7a270d0..ed6a8c6 100644
--- a/src/cmd/go/testdata/script/mod_bad_domain.txt
+++ b/src/cmd/go/testdata/script/mod_bad_domain.txt
@@ -2,7 +2,7 @@
 
 # explicit get should report errors about bad names
 ! go get appengine
-stderr '^go get: malformed module path "appengine": missing dot in first path element$'
+stderr '^go: malformed module path "appengine": missing dot in first path element$'
 ! go get x/y.z
 stderr 'malformed module path "x/y.z": missing dot in first path element'
 
diff --git a/src/cmd/go/testdata/script/mod_dot.txt b/src/cmd/go/testdata/script/mod_dot.txt
index ca8d5c6..cb60e98 100644
--- a/src/cmd/go/testdata/script/mod_dot.txt
+++ b/src/cmd/go/testdata/script/mod_dot.txt
@@ -5,11 +5,11 @@
 # to resolve an external module.
 cd dir
 ! go get
-stderr '^go get: no package in current directory$'
+stderr '^go: no package to get in current directory$'
 ! go get .
-stderr '^go get \.: no package in current directory$'
+stderr '^go: .: no package to get in current directory$'
 ! go get ./subdir
-stderr '^go get: \.[/\\]subdir \('$WORK'[/\\]gopath[/\\]src[/\\]dir[/\\]subdir\) is not a package in module rooted at '$WORK'[/\\]gopath[/\\]src[/\\]dir$'
+stderr '^go: \.[/\\]subdir \('$WORK'[/\\]gopath[/\\]src[/\\]dir[/\\]subdir\) is not a package in module rooted at '$WORK'[/\\]gopath[/\\]src[/\\]dir$'
 ! go list
 ! stderr 'cannot find module providing package'
 stderr '^no Go files in '$WORK'[/\\]gopath[/\\]src[/\\]dir$'
diff --git a/src/cmd/go/testdata/script/mod_download.txt b/src/cmd/go/testdata/script/mod_download.txt
index c2b72b2..89e58a2 100644
--- a/src/cmd/go/testdata/script/mod_download.txt
+++ b/src/cmd/go/testdata/script/mod_download.txt
@@ -93,19 +93,19 @@
 
 # download reports errors encountered when locating modules
 ! go mod download bad/path
-stderr '^go mod download: module bad/path: not a known dependency$'
+stderr '^go: module bad/path: not a known dependency$'
 ! go mod download bad/path@latest
-stderr '^go mod download: bad/path@latest: malformed module path "bad/path": missing dot in first path element$'
+stderr '^go: bad/path@latest: malformed module path "bad/path": missing dot in first path element$'
 ! go mod download rsc.io/quote@v1.999.999
-stderr '^go mod download: rsc.io/quote@v1.999.999: reading .*/v1.999.999.info: 404 Not Found$'
+stderr '^go: rsc.io/quote@v1.999.999: reading .*/v1.999.999.info: 404 Not Found$'
 ! go mod download -json bad/path
 stdout '^\t"Error": "module bad/path: not a known dependency"'
 
 # download main module produces a warning or error
 go mod download m
-stderr '^go mod download: skipping argument m that resolves to the main module\n'
+stderr '^go: skipping download of m that resolves to the main module\n'
 ! go mod download m@latest
-stderr '^go mod download: m@latest: malformed module path "m": missing dot in first path element$'
+stderr '^go: m@latest: malformed module path "m": missing dot in first path element$'
 
 # download without arguments updates go.mod and go.sum after loading the
 # build list, but does not save sums for downloaded zips.
diff --git a/src/cmd/go/testdata/script/mod_edit.txt b/src/cmd/go/testdata/script/mod_edit.txt
index 5aa5ca1..ebc032a 100644
--- a/src/cmd/go/testdata/script/mod_edit.txt
+++ b/src/cmd/go/testdata/script/mod_edit.txt
@@ -23,18 +23,18 @@
 
 # -exclude and -retract reject invalid versions.
 ! go mod edit -exclude=example.com/m@bad
-stderr '^go mod: -exclude=example.com/m@bad: version "bad" invalid: must be of the form v1.2.3$'
+stderr '^go: -exclude=example.com/m@bad: version "bad" invalid: must be of the form v1.2.3$'
 ! go mod edit -retract=bad
-stderr '^go mod: -retract=bad: version "bad" invalid: must be of the form v1.2.3$'
+stderr '^go: -retract=bad: version "bad" invalid: must be of the form v1.2.3$'
 
 ! go mod edit -exclude=example.com/m@v2.0.0
-stderr '^go mod: -exclude=example.com/m@v2\.0\.0: version "v2\.0\.0" invalid: should be v2\.0\.0\+incompatible \(or module example\.com/m/v2\)$'
+stderr '^go: -exclude=example.com/m@v2\.0\.0: version "v2\.0\.0" invalid: should be v2\.0\.0\+incompatible \(or module example\.com/m/v2\)$'
 
 ! go mod edit -exclude=example.com/m/v2@v1.0.0
-stderr '^go mod: -exclude=example.com/m/v2@v1\.0\.0: version "v1\.0\.0" invalid: should be v2, not v1$'
+stderr '^go: -exclude=example.com/m/v2@v1\.0\.0: version "v1\.0\.0" invalid: should be v2, not v1$'
 
 ! go mod edit -exclude=gopkg.in/example.v1@v2.0.0
-stderr '^go mod: -exclude=gopkg\.in/example\.v1@v2\.0\.0: version "v2\.0\.0" invalid: should be v1, not v2$'
+stderr '^go: -exclude=gopkg\.in/example\.v1@v2\.0\.0: version "v2\.0\.0" invalid: should be v1, not v2$'
 
 cmpenv go.mod $WORK/go.mod.edit2
 
diff --git a/src/cmd/go/testdata/script/mod_get_changes.txt b/src/cmd/go/testdata/script/mod_get_changes.txt
index 3287b2a..2829111 100644
--- a/src/cmd/go/testdata/script/mod_get_changes.txt
+++ b/src/cmd/go/testdata/script/mod_get_changes.txt
@@ -4,8 +4,8 @@
 go list -m all
 ! stdout golang.org/x/text
 go get -d rsc.io/quote@v1.5.2
-stderr '^go get: added rsc.io/quote v1.5.2$'
-stderr '^go get: upgraded rsc.io/sampler v1.0.0 => v1.3.0$'
+stderr '^go: added rsc.io/quote v1.5.2$'
+stderr '^go: upgraded rsc.io/sampler v1.0.0 => v1.3.0$'
 ! stderr '^go get.*golang.org/x/text'
 go list -m all
 stdout golang.org/x/text
@@ -15,8 +15,8 @@
 # and for changed explicit dependencies. 'go get' does not print messages
 # for changed indirect dependencies.
 go get -d rsc.io/sampler@none
-stderr '^go get: downgraded rsc.io/quote v1.5.2 => v1.3.0$'
-stderr '^go get: removed rsc.io/sampler v1.3.0$'
+stderr '^go: downgraded rsc.io/quote v1.5.2 => v1.3.0$'
+stderr '^go: removed rsc.io/sampler v1.3.0$'
 ! stderr '^go get.*golang.org/x/text'
 cmp go.mod go.mod.downgrade
 
@@ -24,8 +24,8 @@
 # for explicit dependencies removed as a consequence.
 cp go.mod.usequote go.mod
 go get -d rsc.io/quote@v1.5.1
-stderr '^go get: downgraded rsc.io/quote v1.5.2 => v1.5.1$'
-stderr '^go get: removed usequote v0.0.0$'
+stderr '^go: downgraded rsc.io/quote v1.5.2 => v1.5.1$'
+stderr '^go: removed usequote v0.0.0$'
 
 -- go.mod --
 module m
diff --git a/src/cmd/go/testdata/script/mod_get_deprecate_install.txt b/src/cmd/go/testdata/script/mod_get_deprecate_install.txt
index 63cd27a..e8142af 100644
--- a/src/cmd/go/testdata/script/mod_get_deprecate_install.txt
+++ b/src/cmd/go/testdata/script/mod_get_deprecate_install.txt
@@ -4,7 +4,7 @@
 
 # 'go get' outside a module with an executable prints a deprecation message.
 go get example.com/cmd/a
-stderr '^go get: installing executables with ''go get'' in module mode is deprecated.$'
+stderr '^go: installing executables with ''go get'' in module mode is deprecated.$'
 stderr 'Use ''go install pkg@version'' instead.'
 
 cp go.mod.orig go.mod
@@ -18,7 +18,7 @@
 # 'go get' inside a module with an executable prints a different
 # deprecation message.
 go get example.com/cmd/a
-stderr '^go get: installing executables with ''go get'' in module mode is deprecated.$'
+stderr '^go: installing executables with ''go get'' in module mode is deprecated.$'
 stderr 'To adjust and download dependencies of the current module, use ''go get -d'''
 cp go.mod.orig go.mod
 
diff --git a/src/cmd/go/testdata/script/mod_get_downgrade.txt b/src/cmd/go/testdata/script/mod_get_downgrade.txt
index c26c5e1..685bde7 100644
--- a/src/cmd/go/testdata/script/mod_get_downgrade.txt
+++ b/src/cmd/go/testdata/script/mod_get_downgrade.txt
@@ -20,8 +20,8 @@
 stdout 'rsc.io/sampler v1.3.0'
 
 ! go get -d rsc.io/sampler@v1.0.0 rsc.io/quote@v1.5.2 golang.org/x/text@none
-stderr -count=1 '^go get:'
-stderr '^go get: rsc.io/quote@v1.5.2 requires rsc.io/sampler@v1.3.0, not rsc.io/sampler@v1.0.0$'
+! stderr add|remove|upgrad|downgrad
+stderr '^go: rsc.io/quote@v1.5.2 requires rsc.io/sampler@v1.3.0, not rsc.io/sampler@v1.0.0$'
 
 go list -m all
 stdout 'rsc.io/quote v1.5.1'
diff --git a/src/cmd/go/testdata/script/mod_get_downgrade_missing.txt b/src/cmd/go/testdata/script/mod_get_downgrade_missing.txt
index 5b768fa..2068cae 100644
--- a/src/cmd/go/testdata/script/mod_get_downgrade_missing.txt
+++ b/src/cmd/go/testdata/script/mod_get_downgrade_missing.txt
@@ -5,7 +5,7 @@
 # rather than a "matched no packages" warning.
 
 ! go get -d example.net/pkgadded@v1.1.0 example.net/pkgadded/subpkg/...
-stderr '^go get: example.net/pkgadded@v1.1.0 conflicts with example.net/pkgadded/subpkg/...@upgrade \(v1.2.0\)$'
+stderr '^go: example.net/pkgadded@v1.1.0 conflicts with example.net/pkgadded/subpkg/...@upgrade \(v1.2.0\)$'
 ! stderr 'matched no packages'
 cmp go.mod.orig go.mod
 
diff --git a/src/cmd/go/testdata/script/mod_get_go_file.txt b/src/cmd/go/testdata/script/mod_get_go_file.txt
index 0c7b5dc..35a77a9 100644
--- a/src/cmd/go/testdata/script/mod_get_go_file.txt
+++ b/src/cmd/go/testdata/script/mod_get_go_file.txt
@@ -17,7 +17,7 @@
 
 # argument has .go suffix, is a file and exists
 ! go get test.go
-stderr 'go get test.go: arguments must be package or module paths'
+stderr 'go: test.go: arguments must be package or module paths'
 
 # argument has .go suffix, doesn't exist and has no slashes
 ! go get test_missing.go
@@ -25,7 +25,7 @@
 
 # argument has .go suffix, is a file and exists in sub-directory
 ! go get test/test.go
-stderr 'go get: test/test.go exists as a file, but ''go get'' requires package arguments'
+stderr 'go: test/test.go exists as a file, but ''go get'' requires package arguments'
 
 # argument has .go suffix, doesn't exist and has slashes
 ! go get test/test_missing.go
@@ -35,19 +35,19 @@
 # argument has .go suffix, is a symlink and exists
 [symlink] symlink test_sym.go -> test.go
 [symlink] ! go get test_sym.go
-[symlink] stderr 'go get test_sym.go: arguments must be package or module paths'
+[symlink] stderr 'go: test_sym.go: arguments must be package or module paths'
 [symlink] rm test_sym.go
 
 # argument has .go suffix, is a symlink and exists in sub-directory
 [symlink] symlink test/test_sym.go -> test.go
 [symlink] ! go get test/test_sym.go
-[symlink] stderr 'go get: test/test_sym.go exists as a file, but ''go get'' requires package arguments'
+[symlink] stderr 'go: test/test_sym.go exists as a file, but ''go get'' requires package arguments'
 [symlink] rm test_sym.go
 
 # argument has .go suffix, is a directory and exists
 mkdir test_dir.go
 ! go get test_dir.go
-stderr 'go get test_dir.go: arguments must be package or module paths'
+stderr 'go: test_dir.go: arguments must be package or module paths'
 rm test_dir.go
 
 # argument has .go suffix, is a directory and exists in sub-directory
diff --git a/src/cmd/go/testdata/script/mod_get_main.txt b/src/cmd/go/testdata/script/mod_get_main.txt
index 50b2fee..5c9b762 100644
--- a/src/cmd/go/testdata/script/mod_get_main.txt
+++ b/src/cmd/go/testdata/script/mod_get_main.txt
@@ -3,13 +3,13 @@
 
 # relative and absolute paths must be within the main module.
 ! go get -d ..
-stderr '^go get: \.\. \('$WORK'[/\\]gopath\) is not within module rooted at '$WORK'[/\\]gopath[/\\]src$'
+stderr '^go: \.\. \('$WORK'[/\\]gopath\) is not within module rooted at '$WORK'[/\\]gopath[/\\]src$'
 ! go get -d $WORK
-stderr '^go get: '$WORK' is not within module rooted at '$WORK'[/\\]gopath[/\\]src$'
+stderr '^go: '$WORK' is not within module rooted at '$WORK'[/\\]gopath[/\\]src$'
 ! go get -d ../...
-stderr '^go get: \.\./\.\.\. \('$WORK'[/\\]gopath([/\\]...)?\) is not within module rooted at '$WORK'[/\\]gopath[/\\]src$'
+stderr '^go: \.\./\.\.\. \('$WORK'[/\\]gopath([/\\]...)?\) is not within module rooted at '$WORK'[/\\]gopath[/\\]src$'
 ! go get -d $WORK/...
-stderr '^go get: '$WORK'[/\\]\.\.\. is not within module rooted at '$WORK'[/\\]gopath[/\\]src$'
+stderr '^go: '$WORK'[/\\]\.\.\. is not within module rooted at '$WORK'[/\\]gopath[/\\]src$'
 
 # @patch and @latest within the main module refer to the current version.
 # The main module won't be upgraded, but missing dependencies will be added.
@@ -31,15 +31,15 @@
 
 # The main module cannot be updated to a specific version.
 ! go get -d rsc.io@v0.1.0
-stderr '^go get: can''t request version "v0.1.0" of the main module \(rsc.io\)$'
+stderr '^go: can''t request version "v0.1.0" of the main module \(rsc.io\)$'
 
 # A package in the main module can't be upgraded either.
 ! go get -d rsc.io/x@v0.1.0
-stderr '^go get: package rsc.io/x is in the main module, so can''t request version v0.1.0$'
+stderr '^go: package rsc.io/x is in the main module, so can''t request version v0.1.0$'
 
 # Nor can a pattern matching packages in the main module.
 ! go get -d rsc.io/x/...@latest
-stderr '^go get: pattern rsc.io/x/... matches package rsc.io/x in the main module, so can''t request version latest$'
+stderr '^go: pattern rsc.io/x/... matches package rsc.io/x in the main module, so can''t request version latest$'
 
 -- go.mod.orig --
 module rsc.io
diff --git a/src/cmd/go/testdata/script/mod_get_newcycle.txt b/src/cmd/go/testdata/script/mod_get_newcycle.txt
index f71620c..18dc650 100644
--- a/src/cmd/go/testdata/script/mod_get_newcycle.txt
+++ b/src/cmd/go/testdata/script/mod_get_newcycle.txt
@@ -11,4 +11,4 @@
 cmp stderr stderr-expected
 
 -- stderr-expected --
-go get: example.com/newcycle/a@v1.0.0 requires example.com/newcycle/a@v1.0.1, not example.com/newcycle/a@v1.0.0
+go: example.com/newcycle/a@v1.0.0 requires example.com/newcycle/a@v1.0.1, not example.com/newcycle/a@v1.0.0
diff --git a/src/cmd/go/testdata/script/mod_get_nopkgs.txt b/src/cmd/go/testdata/script/mod_get_nopkgs.txt
index 078e71a..2711f93 100644
--- a/src/cmd/go/testdata/script/mod_get_nopkgs.txt
+++ b/src/cmd/go/testdata/script/mod_get_nopkgs.txt
@@ -16,7 +16,7 @@
 
 ! go get -d example.net/emptysubdir/subdir/...
 ! stderr 'matched no packages'
-stderr '^go get example\.net/emptysubdir/subdir/\.\.\.: module example\.net/emptysubdir/subdir: reading http://.*: 404 Not Found\n\tserver response: 404 page not found\n\z'
+stderr '^go: example\.net/emptysubdir/subdir/\.\.\.: module example\.net/emptysubdir/subdir: reading http://.*: 404 Not Found\n\tserver response: 404 page not found\n\z'
 
 # It doesn't make sense to 'go get' a path in the standard library,
 # since the standard library necessarily can't have unresolved imports.
@@ -27,7 +27,7 @@
 # which isn't ideal either.
 
 ! go get -d builtin/...  # in GOROOT/src, but contains no packages
-stderr '^go get builtin/...: malformed module path "builtin": missing dot in first path element$'
+stderr '^go: builtin/...: malformed module path "builtin": missing dot in first path element$'
 
 -- go.mod --
 module example.net/emptysubdir
diff --git a/src/cmd/go/testdata/script/mod_get_patch.txt b/src/cmd/go/testdata/script/mod_get_patch.txt
index 053ef62..5957a36 100644
--- a/src/cmd/go/testdata/script/mod_get_patch.txt
+++ b/src/cmd/go/testdata/script/mod_get_patch.txt
@@ -8,7 +8,7 @@
 # at the start of 'go get', not the version after applying other changes.
 
 ! go get -d example.net/a@v0.2.0 example.net/b@patch
-stderr '^go get: example.net/a@v0.2.0 requires example.net/b@v0.2.0, not example.net/b@patch \(v0.1.1\)$'
+stderr '^go: example.net/a@v0.2.0 requires example.net/b@v0.2.0, not example.net/b@patch \(v0.1.1\)$'
 cmp go.mod go.mod.orig
 
 
@@ -19,7 +19,7 @@
 # TODO(#42360): Reconsider the change in defaults.
 
 ! go get -d -u=patch example.net/a@v0.2.0 example.net/b
-stderr '^go get: example.net/a@v0.2.0 requires example.net/b@v0.2.0, not example.net/b@patch \(v0.1.1\)$'
+stderr '^go: example.net/a@v0.2.0 requires example.net/b@v0.2.0, not example.net/b@patch \(v0.1.1\)$'
 cmp go.mod go.mod.orig
 
 
@@ -38,7 +38,7 @@
 
 cp go.mod.orig go.mod
 ! go get -u=patch all
-stderr '^go get: example.net/a@v0.1.1 \(matching all@patch\) requires example.net/b@v0.2.0, not example.net/b@v0.1.1 \(matching all@patch\)$'
+stderr '^go: example.net/a@v0.1.1 \(matching all@patch\) requires example.net/b@v0.2.0, not example.net/b@v0.1.1 \(matching all@patch\)$'
 cmp go.mod go.mod.orig
 
 
diff --git a/src/cmd/go/testdata/script/mod_get_patchcycle.txt b/src/cmd/go/testdata/script/mod_get_patchcycle.txt
index d1db56f..6600109 100644
--- a/src/cmd/go/testdata/script/mod_get_patchcycle.txt
+++ b/src/cmd/go/testdata/script/mod_get_patchcycle.txt
@@ -6,7 +6,7 @@
 # (It used to print v0.1.1 but then silently upgrade to v0.2.0.)
 
 ! go get example.net/a@patch
-stderr '^go get: example.net/a@patch \(v0.1.1\) requires example.net/a@v0.2.0, not example.net/a@patch \(v0.1.1\)$'  # TODO: A mention of b v0.1.0 would be nice.
+stderr '^go: example.net/a@patch \(v0.1.1\) requires example.net/a@v0.2.0, not example.net/a@patch \(v0.1.1\)$'  # TODO: A mention of b v0.1.0 would be nice.
 
 -- go.mod --
 module example
diff --git a/src/cmd/go/testdata/script/mod_get_patchmod.txt b/src/cmd/go/testdata/script/mod_get_patchmod.txt
index e39d13a..bc1859e 100644
--- a/src/cmd/go/testdata/script/mod_get_patchmod.txt
+++ b/src/cmd/go/testdata/script/mod_get_patchmod.txt
@@ -16,7 +16,7 @@
 # not upgraded to the latest patch of the new transitive dependency.
 
 ! go get -d example.net/pkgremoved@patch example.net/other@v0.1.0
-stderr '^go get: example.net/other@v0.1.0 requires example.net/pkgremoved@v0.2.0, not example.net/pkgremoved@patch \(v0.1.1\)$'
+stderr '^go: example.net/other@v0.1.0 requires example.net/pkgremoved@v0.2.0, not example.net/pkgremoved@patch \(v0.1.1\)$'
 cmp go.mod.orig go.mod
 
 
diff --git a/src/cmd/go/testdata/script/mod_get_patterns.txt b/src/cmd/go/testdata/script/mod_get_patterns.txt
index aee4374..3b5ab43 100644
--- a/src/cmd/go/testdata/script/mod_get_patterns.txt
+++ b/src/cmd/go/testdata/script/mod_get_patterns.txt
@@ -10,11 +10,11 @@
 
 cp go.mod.orig go.mod
 ! go get -d rsc.io/quote/x...
-stderr 'go get: module rsc.io/quote@upgrade found \(v1.5.2\), but does not contain packages matching rsc.io/quote/x...'
+stderr 'go: module rsc.io/quote@upgrade found \(v1.5.2\), but does not contain packages matching rsc.io/quote/x...'
 ! grep 'require rsc.io/quote' go.mod
 
 ! go get -d rsc.io/quote/x/...
-stderr 'go get: module rsc.io/quote@upgrade found \(v1.5.2\), but does not contain packages matching rsc.io/quote/x/...'
+stderr 'go: module rsc.io/quote@upgrade found \(v1.5.2\), but does not contain packages matching rsc.io/quote/x/...'
 ! grep 'require rsc.io/quote' go.mod
 
 # If a pattern matches no packages within a module, the module should not
diff --git a/src/cmd/go/testdata/script/mod_get_pkgtags.txt b/src/cmd/go/testdata/script/mod_get_pkgtags.txt
index 0c79ec7..2e2ab72 100644
--- a/src/cmd/go/testdata/script/mod_get_pkgtags.txt
+++ b/src/cmd/go/testdata/script/mod_get_pkgtags.txt
@@ -59,7 +59,7 @@
 # but fail for a non-package subdirectory of a module.
 
 ! go get -d example.net/missing/subdir@v0.1.0
-stderr '^go get: module example.net/missing@v0.1.0 found \(replaced by ./missing\), but does not contain package example.net/missing/subdir$'
+stderr '^go: module example.net/missing@v0.1.0 found \(replaced by ./missing\), but does not contain package example.net/missing/subdir$'
 
 go get -d example.net/missing@v0.1.0
 
@@ -68,7 +68,7 @@
 # module is already present in the build list.
 
 ! go get -d example.net/missing/subdir@v0.1.0
-stderr '^go get: module example.net/missing@v0.1.0 found \(replaced by ./missing\), but does not contain package example.net/missing/subdir$'
+stderr '^go: module example.net/missing@v0.1.0 found \(replaced by ./missing\), but does not contain package example.net/missing/subdir$'
 
 
 -- go.mod --
diff --git a/src/cmd/go/testdata/script/mod_get_private_vcs.txt b/src/cmd/go/testdata/script/mod_get_private_vcs.txt
index 75c776a..c8862f4 100644
--- a/src/cmd/go/testdata/script/mod_get_private_vcs.txt
+++ b/src/cmd/go/testdata/script/mod_get_private_vcs.txt
@@ -13,7 +13,7 @@
 # Fetching a nonexistent commit should return an "unknown revision"
 # error message.
 ! go get github.com/golang/term@86186f3aba07ed0212cfb944f3398997d2d07c6b
-stderr '^go get: github.com/golang/term@86186f3aba07ed0212cfb944f3398997d2d07c6b: invalid version: unknown revision 86186f3aba07ed0212cfb944f3398997d2d07c6b$'
+stderr '^go: github.com/golang/term@86186f3aba07ed0212cfb944f3398997d2d07c6b: invalid version: unknown revision 86186f3aba07ed0212cfb944f3398997d2d07c6b$'
 ! stdout .
 
 ! go get github.com/golang/nonexist@master
diff --git a/src/cmd/go/testdata/script/mod_get_replaced.txt b/src/cmd/go/testdata/script/mod_get_replaced.txt
index d97f3f1..ab21bd5 100644
--- a/src/cmd/go/testdata/script/mod_get_replaced.txt
+++ b/src/cmd/go/testdata/script/mod_get_replaced.txt
@@ -82,7 +82,7 @@
 ! go list example
 stderr '^package example is not in GOROOT \(.*\)$'
 ! go get -d example
-stderr '^go get: malformed module path "example": missing dot in first path element$'
+stderr '^go: malformed module path "example": missing dot in first path element$'
 
 go mod edit -replace example@v0.1.0=./example
 
diff --git a/src/cmd/go/testdata/script/mod_get_split.txt b/src/cmd/go/testdata/script/mod_get_split.txt
index f4e7661..2fb88ab 100644
--- a/src/cmd/go/testdata/script/mod_get_split.txt
+++ b/src/cmd/go/testdata/script/mod_get_split.txt
@@ -55,7 +55,7 @@
 # TODO(#27899): Should we instead upgrade or downgrade to an arbirary version?
 
 ! go get -d example.net/split/nested/...@v0.1.0
-stderr '^go get: example.net/split/nested/\.\.\.@v0.1.0 matches packages in example.net/split@v0.2.0 but not example.net/split@v0.1.0: specify a different version for module example.net/split$'
+stderr '^go: example.net/split/nested/\.\.\.@v0.1.0 matches packages in example.net/split@v0.2.0 but not example.net/split@v0.1.0: specify a different version for module example.net/split$'
 
 cmp go.mod go.mod.orig
 
diff --git a/src/cmd/go/testdata/script/mod_get_svn.txt b/src/cmd/go/testdata/script/mod_get_svn.txt
index 3817fce..4d6b94ae 100644
--- a/src/cmd/go/testdata/script/mod_get_svn.txt
+++ b/src/cmd/go/testdata/script/mod_get_svn.txt
@@ -27,7 +27,7 @@
 # reasonable message instead of a panic.
 ! go get -d vcs-test.golang.org/svn/nonexistent.svn
 ! stderr panic
-stderr 'go get vcs-test.golang.org/svn/nonexistent.svn: no matching versions for query "upgrade"'
+stderr 'go: vcs-test.golang.org/svn/nonexistent.svn: no matching versions for query "upgrade"'
 
 -- go.mod --
 module golang/go/issues/28943/main
diff --git a/src/cmd/go/testdata/script/mod_get_wild.txt b/src/cmd/go/testdata/script/mod_get_wild.txt
index 78c645c..b88f268 100644
--- a/src/cmd/go/testdata/script/mod_get_wild.txt
+++ b/src/cmd/go/testdata/script/mod_get_wild.txt
@@ -12,7 +12,7 @@
 # from attempting to resolve a new module whose path is a prefix of the pattern.
 
 ! go get -d -u=patch example.../b@upgrade
-stderr '^go get: no modules to query for example\.\.\./b@upgrade because first path element contains a wildcard$'
+stderr '^go: no modules to query for example\.\.\./b@upgrade because first path element contains a wildcard$'
 
 
 # Patching . causes a patch to example.net/a, which introduces a new match
diff --git a/src/cmd/go/testdata/script/mod_getmode_vendor.txt b/src/cmd/go/testdata/script/mod_getmode_vendor.txt
index 00070c0..a4e23ac 100644
--- a/src/cmd/go/testdata/script/mod_getmode_vendor.txt
+++ b/src/cmd/go/testdata/script/mod_getmode_vendor.txt
@@ -11,16 +11,16 @@
 stdout '^golang.org/x/text v0.0.0.* .*vendor[\\/]golang.org[\\/]x[\\/]text[\\/]language$'
 
 ! go list -mod=vendor -m rsc.io/quote@latest
-stderr 'go list -m: rsc.io/quote@latest: cannot query module due to -mod=vendor'
+stderr 'go: rsc.io/quote@latest: cannot query module due to -mod=vendor'
 ! go get -mod=vendor -u
 stderr 'flag provided but not defined: -mod'
 
 # Since we don't have a complete module graph, 'go list -m' queries
 # that require the complete graph should fail with a useful error.
 ! go list -mod=vendor -m all
-stderr 'go list -m: can''t compute ''all'' using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)'
+stderr 'go: can''t compute ''all'' using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)'
 ! go list -mod=vendor -m ...
-stderr 'go list -m: can''t match module patterns using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)'
+stderr 'go: can''t match module patterns using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)'
 
 -- go.mod --
 module x
diff --git a/src/cmd/go/testdata/script/mod_gonoproxy.txt b/src/cmd/go/testdata/script/mod_gonoproxy.txt
index 2047869..1909400 100644
--- a/src/cmd/go/testdata/script/mod_gonoproxy.txt
+++ b/src/cmd/go/testdata/script/mod_gonoproxy.txt
@@ -27,13 +27,13 @@
 # When GOPROXY is not empty but contains no entries, an error should be reported.
 env GOPROXY=','
 ! go get -d golang.org/x/text
-stderr '^go get golang.org/x/text: GOPROXY list is not the empty string, but contains no entries$'
+stderr '^go: golang.org/x/text: GOPROXY list is not the empty string, but contains no entries$'
 
 # When GOPROXY=off, fetching modules not matched by GONOPROXY fails.
 env GONOPROXY=*/fortune
 env GOPROXY=off
 ! go get -d golang.org/x/text
-stderr '^go get golang.org/x/text: module lookup disabled by GOPROXY=off$'
+stderr '^go: golang.org/x/text: module lookup disabled by GOPROXY=off$'
 
 # GONOPROXY bypasses proxy
 [!net] skip
diff --git a/src/cmd/go/testdata/script/mod_install_pkg_version.txt b/src/cmd/go/testdata/script/mod_install_pkg_version.txt
index fd02392..1ee68e7 100644
--- a/src/cmd/go/testdata/script/mod_install_pkg_version.txt
+++ b/src/cmd/go/testdata/script/mod_install_pkg_version.txt
@@ -16,7 +16,7 @@
 cd m
 cp go.mod go.mod.orig
 ! go list -m all
-stderr '^go list -m: example.com/cmd@v1.1.0-doesnotexist: missing go.sum entry; to add it:\n\tgo mod download example.com/cmd$'
+stderr '^go: example.com/cmd@v1.1.0-doesnotexist: missing go.sum entry; to add it:\n\tgo mod download example.com/cmd$'
 go install example.com/cmd/a@latest
 cmp go.mod go.mod.orig
 exists $GOPATH/bin/a$GOEXE
@@ -81,15 +81,15 @@
 # 'go install pkg@version' reports errors for meta packages, std packages,
 # and directories.
 ! go install std@v1.0.0
-stderr '^go install: std@v1.0.0: argument must be a package path, not a meta-package$'
+stderr '^go: std@v1.0.0: argument must be a package path, not a meta-package$'
 ! go install fmt@v1.0.0
-stderr '^go install: fmt@v1.0.0: argument must not be a package in the standard library$'
+stderr '^go: fmt@v1.0.0: argument must not be a package in the standard library$'
 ! go install example.com//cmd/a@v1.0.0
-stderr '^go install: example.com//cmd/a@v1.0.0: argument must be a clean package path$'
+stderr '^go: example.com//cmd/a@v1.0.0: argument must be a clean package path$'
 ! go install example.com/cmd/a@v1.0.0 ./x@v1.0.0
-stderr '^go install: ./x@v1.0.0: argument must be a package path, not a relative path$'
+stderr '^go: ./x@v1.0.0: argument must be a package path, not a relative path$'
 ! go install example.com/cmd/a@v1.0.0 $GOPATH/src/x@v1.0.0
-stderr '^go install: '$WORK'[/\\]gopath/src/x@v1.0.0: argument must be a package path, not an absolute path$'
+stderr '^go: '$WORK'[/\\]gopath/src/x@v1.0.0: argument must be a package path, not an absolute path$'
 ! go install example.com/cmd/a@v1.0.0 cmd/...@v1.0.0
 stderr '^package cmd/go not provided by module example.com/cmd@v1.0.0$'
 
@@ -106,7 +106,7 @@
 env GO111MODULE=auto
 
 ! go install example.com/cmd/a@v1.0.0 example.com/cmd/b@latest
-stderr '^go install: example.com/cmd/b@latest: all arguments must have the same version \(@v1.0.0\)$'
+stderr '^go: example.com/cmd/b@latest: all arguments must have the same version \(@v1.0.0\)$'
 
 
 # 'go install pkg@version' should report an error if the arguments are in
@@ -137,7 +137,7 @@
 
 # If a wildcard matches no packages, we should see a warning.
 ! go install example.com/cmd/nomatch...@v1.0.0
-stderr '^go install: example.com/cmd/nomatch\.\.\.@v1.0.0: module example.com/cmd@v1.0.0 found, but does not contain packages matching example.com/cmd/nomatch\.\.\.$'
+stderr '^go: example.com/cmd/nomatch\.\.\.@v1.0.0: module example.com/cmd@v1.0.0 found, but does not contain packages matching example.com/cmd/nomatch\.\.\.$'
 go install example.com/cmd/a@v1.0.0 example.com/cmd/nomatch...@v1.0.0
 stderr '^go: warning: "example.com/cmd/nomatch\.\.\." matched no packages$'
 
@@ -159,7 +159,7 @@
 # 'go install pkg@version' should report an error if the module requires a
 # higher version of itself.
 ! go install example.com/cmd/a@v1.0.0-newerself
-stderr '^go install: example.com/cmd/a@v1.0.0-newerself: version constraints conflict:\n\texample.com/cmd@v1.0.0-newerself requires example.com/cmd@v1.0.0, but example.com/cmd@v1.0.0-newerself is requested$'
+stderr '^go: example.com/cmd/a@v1.0.0-newerself: version constraints conflict:\n\texample.com/cmd@v1.0.0-newerself requires example.com/cmd@v1.0.0, but example.com/cmd@v1.0.0-newerself is requested$'
 
 
 # 'go install pkg@version' will only match a retracted version if it's
@@ -192,12 +192,12 @@
 
 func main() {}
 -- replace-err --
-go install: example.com/cmd/a@v1.0.0-replace (in example.com/cmd@v1.0.0-replace):
+go: example.com/cmd/a@v1.0.0-replace (in example.com/cmd@v1.0.0-replace):
 	The go.mod file for the module providing named packages contains one or
 	more replace directives. It must not contain directives that would cause
 	it to be interpreted differently than if it were the main module.
 -- exclude-err --
-go install: example.com/cmd/a@v1.0.0-exclude (in example.com/cmd@v1.0.0-exclude):
+go: example.com/cmd/a@v1.0.0-exclude (in example.com/cmd@v1.0.0-exclude):
 	The go.mod file for the module providing named packages contains one or
 	more exclude directives. It must not contain directives that would cause
 	it to be interpreted differently than if it were the main module.
diff --git a/src/cmd/go/testdata/script/mod_invalid_path.txt b/src/cmd/go/testdata/script/mod_invalid_path.txt
index 333a3ff..766e9c0 100644
--- a/src/cmd/go/testdata/script/mod_invalid_path.txt
+++ b/src/cmd/go/testdata/script/mod_invalid_path.txt
@@ -29,7 +29,7 @@
 go list ./use
 stdout '^example.com/dotname/use$'
 ! go list -m example.com/dotname/.dot@latest
-stderr '^go list -m: example.com/dotname/.dot@latest: malformed module path "example.com/dotname/.dot": leading dot in path element$'
+stderr '^go: example.com/dotname/.dot@latest: malformed module path "example.com/dotname/.dot": leading dot in path element$'
 go get -d example.com/dotname/.dot
 go get -d example.com/dotname/use
 go mod tidy
diff --git a/src/cmd/go/testdata/script/mod_invalid_path_plus.txt b/src/cmd/go/testdata/script/mod_invalid_path_plus.txt
index 51dbf93..6a29eb8 100644
--- a/src/cmd/go/testdata/script/mod_invalid_path_plus.txt
+++ b/src/cmd/go/testdata/script/mod_invalid_path_plus.txt
@@ -9,7 +9,7 @@
 
 # 'go list -m' rejects module paths with pluses.
 ! go list -versions -m 'example.net/bad++'
-stderr '^go list -m: malformed module path "example.net/bad\+\+": invalid char ''\+''$'
+stderr '^go: malformed module path "example.net/bad\+\+": invalid char ''\+''$'
 
 # 'go get' accepts package paths with pluses.
 cp go.mod.orig go.mod
diff --git a/src/cmd/go/testdata/script/mod_invalid_version.txt b/src/cmd/go/testdata/script/mod_invalid_version.txt
index 6846a79..31b25f7 100644
--- a/src/cmd/go/testdata/script/mod_invalid_version.txt
+++ b/src/cmd/go/testdata/script/mod_invalid_version.txt
@@ -19,7 +19,7 @@
 go mod edit -require golang.org/x/text@14c0d48ead0c
 cd outside
 ! go list -m golang.org/x/text
-stderr 'go list -m: example.com@v0.0.0 \(replaced by \./\.\.\): parsing ..[/\\]go.mod: '$WORK'[/\\]gopath[/\\]src[/\\]go.mod:5: require golang.org/x/text: version "14c0d48ead0c" invalid: must be of the form v1.2.3'
+stderr 'go: example.com@v0.0.0 \(replaced by \./\.\.\): parsing ..[/\\]go.mod: '$WORK'[/\\]gopath[/\\]src[/\\]go.mod:5: require golang.org/x/text: version "14c0d48ead0c" invalid: must be of the form v1.2.3'
 cd ..
 go list -m golang.org/x/text
 stdout 'golang.org/x/text v0.1.1-0.20170915032832-14c0d48ead0c'
@@ -30,7 +30,7 @@
 go mod edit -require golang.org/x/text/unicode@v0.0.0-20170915032832-14c0d48ead0c
 cd outside
 ! go list -m golang.org/x/text
-stderr 'go list -m: example.com@v0.0.0 requires\n\tgolang.org/x/text/unicode@v0.0.0-20170915032832-14c0d48ead0c: invalid version: missing golang.org/x/text/unicode/go.mod at revision 14c0d48ead0c'
+stderr 'go: example.com@v0.0.0 requires\n\tgolang.org/x/text/unicode@v0.0.0-20170915032832-14c0d48ead0c: invalid version: missing golang.org/x/text/unicode/go.mod at revision 14c0d48ead0c'
 cd ..
 ! go list -m golang.org/x/text
 stderr 'golang.org/x/text/unicode@v0.0.0-20170915032832-14c0d48ead0c: invalid version: missing golang.org/x/text/unicode/go.mod at revision 14c0d48ead0c'
@@ -47,7 +47,7 @@
 go mod edit -require golang.org/x/text@v2.1.1-0.20170915032832-14c0d48ead0c
 cd outside
 ! go list -m golang.org/x/text
-stderr 'go list -m: example.com@v0.0.0 \(replaced by \./\.\.\): parsing ..[/\\]go.mod: '$WORK'[/\\]gopath[/\\]src[/\\]go.mod:5: require golang.org/x/text: version "v2.1.1-0.20170915032832-14c0d48ead0c" invalid: should be v0 or v1, not v2'
+stderr 'go: example.com@v0.0.0 \(replaced by \./\.\.\): parsing ..[/\\]go.mod: '$WORK'[/\\]gopath[/\\]src[/\\]go.mod:5: require golang.org/x/text: version "v2.1.1-0.20170915032832-14c0d48ead0c" invalid: should be v0 or v1, not v2'
 cd ..
 ! go list -m golang.org/x/text
 stderr $WORK'[/\\]gopath[/\\]src[/\\]go.mod:5: require golang.org/x/text: version "v2.1.1-0.20170915032832-14c0d48ead0c" invalid: should be v0 or v1, not v2'
@@ -57,7 +57,7 @@
 go mod edit -require golang.org/x/text@v0.1.1-0.20170915032832-14c0d48ead0
 cd outside
 ! go list -m golang.org/x/text
-stderr 'go list -m: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.1.1-0.20170915032832-14c0d48ead0: invalid pseudo-version: revision is shorter than canonical \(14c0d48ead0c\)'
+stderr 'go: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.1.1-0.20170915032832-14c0d48ead0: invalid pseudo-version: revision is shorter than canonical \(14c0d48ead0c\)'
 cd ..
 ! go list -m golang.org/x/text
 stderr 'golang.org/x/text@v0.1.1-0.20170915032832-14c0d48ead0: invalid pseudo-version: revision is shorter than canonical \(14c0d48ead0c\)'
@@ -67,7 +67,7 @@
 go mod edit -require golang.org/x/text@v0.1.1-0.20170915032832-14c0d48ead0cd47e3104ada247d91be04afc7a5a
 cd outside
 ! go list -m golang.org/x/text
-stderr 'go list -m: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.1.1-0.20170915032832-14c0d48ead0cd47e3104ada247d91be04afc7a5a: invalid pseudo-version: revision is longer than canonical \(14c0d48ead0c\)'
+stderr 'go: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.1.1-0.20170915032832-14c0d48ead0cd47e3104ada247d91be04afc7a5a: invalid pseudo-version: revision is longer than canonical \(14c0d48ead0c\)'
 cd ..
 ! go list -m golang.org/x/text
 stderr 'golang.org/x/text@v0.1.1-0.20170915032832-14c0d48ead0cd47e3104ada247d91be04afc7a5a: invalid pseudo-version: revision is longer than canonical \(14c0d48ead0c\)'
@@ -77,7 +77,7 @@
 go mod edit -require golang.org/x/text@v0.1.1-0.20190915032832-14c0d48ead0c
 cd outside
 ! go list -m golang.org/x/text
-stderr 'go list -m: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.1.1-0.20190915032832-14c0d48ead0c: invalid pseudo-version: does not match version-control timestamp \(expected 20170915032832\)'
+stderr 'go: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.1.1-0.20190915032832-14c0d48ead0c: invalid pseudo-version: does not match version-control timestamp \(expected 20170915032832\)'
 cd ..
 ! go list -m golang.org/x/text
 stderr 'golang.org/x/text@v0.1.1-0.20190915032832-14c0d48ead0c: invalid pseudo-version: does not match version-control timestamp \(expected 20170915032832\)'
@@ -87,7 +87,7 @@
 go mod edit -replace golang.org/x/text@v0.1.1-0.20190915032832-14c0d48ead0c=golang.org/x/text@14c0d48ead0c
 cd outside
 ! go list -m golang.org/x/text
-stderr 'go list -m: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.1.1-0.20190915032832-14c0d48ead0c: invalid pseudo-version: does not match version-control timestamp \(expected 20170915032832\)'
+stderr 'go: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.1.1-0.20190915032832-14c0d48ead0c: invalid pseudo-version: does not match version-control timestamp \(expected 20170915032832\)'
 cd ..
 go list -m golang.org/x/text
 stdout 'golang.org/x/text v0.1.1-0.20190915032832-14c0d48ead0c => golang.org/x/text v0.1.1-0.20170915032832-14c0d48ead0c'
@@ -97,7 +97,7 @@
 go mod edit -require golang.org/x/text@v1.999.999-0.20170915032832-14c0d48ead0c
 cd outside
 ! go list -m golang.org/x/text
-stderr 'go list -m: example.com@v0.0.0 requires\n\tgolang.org/x/text@v1.999.999-0.20170915032832-14c0d48ead0c: invalid pseudo-version: preceding tag \(v1.999.998\) not found'
+stderr 'go: example.com@v0.0.0 requires\n\tgolang.org/x/text@v1.999.999-0.20170915032832-14c0d48ead0c: invalid pseudo-version: preceding tag \(v1.999.998\) not found'
 cd ..
 ! go list -m golang.org/x/text
 stderr 'golang.org/x/text@v1.999.999-0.20170915032832-14c0d48ead0c: invalid pseudo-version: preceding tag \(v1.999.998\) not found'
@@ -109,7 +109,7 @@
 go mod edit -require golang.org/x/text@v1.0.0-20170915032832-14c0d48ead0c
 cd outside
 ! go list -m golang.org/x/text
-stderr 'go list -m: example.com@v0.0.0 requires\n\tgolang.org/x/text@v1.0.0-20170915032832-14c0d48ead0c: invalid pseudo-version: major version without preceding tag must be v0, not v1'
+stderr 'go: example.com@v0.0.0 requires\n\tgolang.org/x/text@v1.0.0-20170915032832-14c0d48ead0c: invalid pseudo-version: major version without preceding tag must be v0, not v1'
 cd ..
 ! go list -m golang.org/x/text
 stderr 'golang.org/x/text@v1.0.0-20170915032832-14c0d48ead0c: invalid pseudo-version: major version without preceding tag must be v0, not v1'
@@ -120,7 +120,7 @@
 go mod edit -require golang.org/x/text@v0.0.0-0.20170915032832-14c0d48ead0c
 cd outside
 ! go list -m golang.org/x/text
-stderr 'go list -m: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.0.0-0.20170915032832-14c0d48ead0c: invalid pseudo-version: version before v0.0.0 would have negative patch number'
+stderr 'go: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.0.0-0.20170915032832-14c0d48ead0c: invalid pseudo-version: version before v0.0.0 would have negative patch number'
 cd ..
 ! go list -m golang.org/x/text
 stderr 'golang.org/x/text@v0.0.0-0.20170915032832-14c0d48ead0c: invalid pseudo-version: version before v0.0.0 would have negative patch number'
@@ -130,7 +130,7 @@
 go mod edit -replace golang.org/x/text@v0.0.0-0.20170915032832-14c0d48ead0c=golang.org/x/text@v0.0.0-20170915032832-14c0d48ead0c
 cd outside
 ! go list -m golang.org/x/text
-stderr 'go list -m: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.0.0-0.20170915032832-14c0d48ead0c: invalid pseudo-version: version before v0.0.0 would have negative patch number'
+stderr 'go: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.0.0-0.20170915032832-14c0d48ead0c: invalid pseudo-version: version before v0.0.0 would have negative patch number'
 cd ..
 go list -m golang.org/x/text
 stdout 'golang.org/x/text v0.0.0-0.20170915032832-14c0d48ead0c => golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c'
@@ -153,7 +153,7 @@
 go mod edit -require golang.org/x/text@v0.2.1-0.20170915032832-14c0d48ead0c
 cd outside
 ! go list -m golang.org/x/text
-stderr 'go list -m: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.2.1-0.20170915032832-14c0d48ead0c: invalid pseudo-version: revision 14c0d48ead0c is not a descendent of preceding tag \(v0.2.0\)'
+stderr 'go: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.2.1-0.20170915032832-14c0d48ead0c: invalid pseudo-version: revision 14c0d48ead0c is not a descendent of preceding tag \(v0.2.0\)'
 cd ..
 ! go list -m golang.org/x/text
 stderr 'golang.org/x/text@v0.2.1-0.20170915032832-14c0d48ead0c: invalid pseudo-version: revision 14c0d48ead0c is not a descendent of preceding tag \(v0.2.0\)'
@@ -163,7 +163,7 @@
 go mod edit -require golang.org/x/text@v0.2.1-0.20171213102548-c4d099d611ac
 cd outside
 ! go list -m golang.org/x/text
-stderr 'go list -m: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.2.1-0.20171213102548-c4d099d611ac: invalid pseudo-version: tag \(v0.2.0\) found on revision c4d099d611ac is already canonical, so should not be replaced with a pseudo-version derived from that tag'
+stderr 'go: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.2.1-0.20171213102548-c4d099d611ac: invalid pseudo-version: tag \(v0.2.0\) found on revision c4d099d611ac is already canonical, so should not be replaced with a pseudo-version derived from that tag'
 cd ..
 ! go list -m golang.org/x/text
 stderr 'golang.org/x/text@v0.2.1-0.20171213102548-c4d099d611ac: invalid pseudo-version: tag \(v0.2.0\) found on revision c4d099d611ac is already canonical, so should not be replaced with a pseudo-version derived from that tag'
@@ -173,7 +173,7 @@
 go mod edit -require golang.org/x/text@v0.1.1-0.20170915032832-14c0d48ead0c+incompatible
 cd outside
 ! go list -m golang.org/x/text
-stderr 'go list -m: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.1.1-0.20170915032832-14c0d48ead0c\+incompatible: invalid version: \+incompatible suffix not allowed: major version v0 is compatible'
+stderr 'go: example.com@v0.0.0 requires\n\tgolang.org/x/text@v0.1.1-0.20170915032832-14c0d48ead0c\+incompatible: invalid version: \+incompatible suffix not allowed: major version v0 is compatible'
 cd ..
 ! go list -m golang.org/x/text
 stderr 'golang.org/x/text@v0.1.1-0.20170915032832-14c0d48ead0c\+incompatible: invalid version: \+incompatible suffix not allowed: major version v0 is compatible'
@@ -194,7 +194,7 @@
 go mod edit -require github.com/pierrec/lz4@v2.0.9-0.20190209155647-9a39efadad3d+incompatible
 cd outside
 ! go list -m github.com/pierrec/lz4
-stderr 'go list -m: example.com@v0.0.0 requires\n\tgithub.com/pierrec/lz4@v2.0.9-0.20190209155647-9a39efadad3d\+incompatible: invalid version: \+incompatible suffix not allowed: module contains a go.mod file, so semantic import versioning is required'
+stderr 'go: example.com@v0.0.0 requires\n\tgithub.com/pierrec/lz4@v2.0.9-0.20190209155647-9a39efadad3d\+incompatible: invalid version: \+incompatible suffix not allowed: module contains a go.mod file, so semantic import versioning is required'
 cd ..
 ! go list -m github.com/pierrec/lz4
 stderr 'github.com/pierrec/lz4@v2.0.9-0.20190209155647-9a39efadad3d\+incompatible: invalid version: \+incompatible suffix not allowed: module contains a go.mod file, so semantic import versioning is required'
@@ -222,7 +222,7 @@
 # not resolve to a pseudo-version with a different major version.
 cp go.mod.orig go.mod
 ! go get -d github.com/pierrec/lz4@v2.0.8
-stderr 'go get: github.com/pierrec/lz4@v2.0.8: invalid version: module contains a go.mod file, so major version must be compatible: should be v0 or v1, not v2'
+stderr 'go: github.com/pierrec/lz4@v2.0.8: invalid version: module contains a go.mod file, so major version must be compatible: should be v0 or v1, not v2'
 
 # An invalid +incompatible suffix for a canonical version should error out,
 # not resolve to a pseudo-version.
diff --git a/src/cmd/go/testdata/script/mod_list.txt b/src/cmd/go/testdata/script/mod_list.txt
index 239c7ca..06316cc 100644
--- a/src/cmd/go/testdata/script/mod_list.txt
+++ b/src/cmd/go/testdata/script/mod_list.txt
@@ -39,8 +39,8 @@
 stdout '^module rsc.io/quote/buggy: not a known dependency$'
 
 ! go list -m nonexist rsc.io/quote/buggy
-stderr '^go list -m: module nonexist: not a known dependency'
-stderr '^go list -m: module rsc.io/quote/buggy: not a known dependency'
+stderr '^go: module nonexist: not a known dependency'
+stderr '^go: module rsc.io/quote/buggy: not a known dependency'
 
 # Module loader does not interfere with list -e (golang.org/issue/24149).
 go list -e -f '{{.Error.Err}}' database
diff --git a/src/cmd/go/testdata/script/mod_list_sums.txt b/src/cmd/go/testdata/script/mod_list_sums.txt
index 86c528f..6c2f57c 100644
--- a/src/cmd/go/testdata/script/mod_list_sums.txt
+++ b/src/cmd/go/testdata/script/mod_list_sums.txt
@@ -29,4 +29,4 @@
 #
 # TODO(#41297): This should not be an error either.
 ! go list -m -mod=readonly -versions rsc.io/sampler
-stderr '^go list -m: rsc\.io/quote@v1\.5\.1: missing go\.sum entry; to add it:\n\tgo mod download rsc\.io/quote$'
+stderr '^go: rsc\.io/quote@v1\.5\.1: missing go\.sum entry; to add it:\n\tgo mod download rsc\.io/quote$'
diff --git a/src/cmd/go/testdata/script/mod_list_update_nolatest.txt b/src/cmd/go/testdata/script/mod_list_update_nolatest.txt
index c6bbbb0..7eebe26 100644
--- a/src/cmd/go/testdata/script/mod_list_update_nolatest.txt
+++ b/src/cmd/go/testdata/script/mod_list_update_nolatest.txt
@@ -26,7 +26,7 @@
 # If proxy returns an invalid response, we should see an error.
 env GOPROXY=$testproxy/invalid
 ! go list -m -u example.com/nolatest
-stderr '^go list -m: loading module retractions for example.com/nolatest@v0.0.0: invalid response from proxy "[^"]*": invalid character ''i'' looking for beginning of value$'
+stderr '^go: loading module retractions for example.com/nolatest@v0.0.0: invalid response from proxy "[^"]*": invalid character ''i'' looking for beginning of value$'
 
 -- go.mod --
 module m
diff --git a/src/cmd/go/testdata/script/mod_load_badchain.txt b/src/cmd/go/testdata/script/mod_load_badchain.txt
index eb464ab..0c4e5e1 100644
--- a/src/cmd/go/testdata/script/mod_load_badchain.txt
+++ b/src/cmd/go/testdata/script/mod_load_badchain.txt
@@ -69,17 +69,17 @@
 
 func Test(t *testing.T) {}
 -- update-main-expected --
-go get: example.com/badchain/c@v1.1.0: parsing go.mod:
+go: example.com/badchain/c@v1.1.0: parsing go.mod:
 	module declares its path as: badchain.example.com/c
 	        but was required as: example.com/badchain/c
 -- update-a-expected --
-go get: example.com/badchain/a@v1.1.0 requires
+go: example.com/badchain/a@v1.1.0 requires
 	example.com/badchain/b@v1.1.0 requires
 	example.com/badchain/c@v1.1.0: parsing go.mod:
 	module declares its path as: badchain.example.com/c
 	        but was required as: example.com/badchain/c
 -- list-expected --
-go list -m: example.com/badchain/a@v1.1.0 requires
+go: example.com/badchain/a@v1.1.0 requires
 	example.com/badchain/b@v1.1.0 requires
 	example.com/badchain/c@v1.1.0: parsing go.mod:
 	module declares its path as: badchain.example.com/c
diff --git a/src/cmd/go/testdata/script/mod_outside.txt b/src/cmd/go/testdata/script/mod_outside.txt
index 3b45594..6da6314 100644
--- a/src/cmd/go/testdata/script/mod_outside.txt
+++ b/src/cmd/go/testdata/script/mod_outside.txt
@@ -135,12 +135,12 @@
 # 'go get -u all' upgrades the transitive import graph of the main module,
 # which is empty.
 ! go get -u all
-stderr '^go get: cannot match "all": go.mod file not found in current directory or any parent directory; see ''go help modules''$'
+stderr '^go: cannot match "all": go.mod file not found in current directory or any parent directory; see ''go help modules''$'
 
 # 'go get' should check the proposed module graph for consistency,
 # even though we won't write it anywhere.
 ! go get -d example.com/printversion@v1.0.0 example.com/version@none
-stderr '^go get: example.com/printversion@v1.0.0 requires example.com/version@v1.0.0, not example.com/version@none$'
+stderr '^go: example.com/printversion@v1.0.0 requires example.com/version@v1.0.0, not example.com/version@none$'
 
 # 'go get -d' should download and extract the source code needed to build the requested version.
 rm -r $GOPATH/pkg/mod/example.com
@@ -196,7 +196,7 @@
 
 # 'go install' should fail if a package argument must be resolved to a module.
 ! go install example.com/printversion
-stderr '^go install: version is required when current directory is not in a module\n\tTry ''go install example.com/printversion@latest'' to install the latest version$'
+stderr '^go: ''go install'' requires a version when current directory is not in a module\n\tTry ''go install example.com/printversion@latest'' to install the latest version$'
 
 # 'go install' should fail if a source file imports a package that must be
 # resolved to a module.
diff --git a/src/cmd/go/testdata/script/mod_prefer_compatible.txt b/src/cmd/go/testdata/script/mod_prefer_compatible.txt
index 1b408c3..8e88997 100644
--- a/src/cmd/go/testdata/script/mod_prefer_compatible.txt
+++ b/src/cmd/go/testdata/script/mod_prefer_compatible.txt
@@ -24,7 +24,7 @@
 stdout '^github.com/russross/blackfriday v1\.'
 
 ! go list -m github.com/russross/blackfriday@patch
-stderr '^go list -m: github.com/russross/blackfriday@patch: can''t query version "patch" of module github.com/russross/blackfriday: no existing version is required$'
+stderr '^go: github.com/russross/blackfriday@patch: can''t query version "patch" of module github.com/russross/blackfriday: no existing version is required$'
 
 # If we're fetching directly from version control, ignored +incompatible
 # versions should also be omitted by 'go list'.
diff --git a/src/cmd/go/testdata/script/mod_proxy_invalid.txt b/src/cmd/go/testdata/script/mod_proxy_invalid.txt
index 6427cc1..63980b8 100644
--- a/src/cmd/go/testdata/script/mod_proxy_invalid.txt
+++ b/src/cmd/go/testdata/script/mod_proxy_invalid.txt
@@ -2,7 +2,7 @@
 env GOPROXY=$GOPROXY/invalid
 
 ! go list -m rsc.io/quote@latest
-stderr '^go list -m: module rsc.io/quote: invalid response from proxy "'$GOPROXY'": invalid character ''i'' looking for beginning of value$'
+stderr '^go: module rsc.io/quote: invalid response from proxy "'$GOPROXY'": invalid character ''i'' looking for beginning of value$'
 
 ! go list -m rsc.io/quote@1.5.2
-stderr '^go list -m: rsc.io/quote@1.5.2: invalid version: invalid response from proxy "'$GOPROXY'": invalid character ''i'' looking for beginning of value$'
+stderr '^go: rsc.io/quote@1.5.2: invalid version: invalid response from proxy "'$GOPROXY'": invalid character ''i'' looking for beginning of value$'
diff --git a/src/cmd/go/testdata/script/mod_query.txt b/src/cmd/go/testdata/script/mod_query.txt
index a75f86e..37587325 100644
--- a/src/cmd/go/testdata/script/mod_query.txt
+++ b/src/cmd/go/testdata/script/mod_query.txt
@@ -25,7 +25,7 @@
 stdout 'rsc.io/quote v1.5.2$'
 
 ! go list -m rsc.io/quote@>v1.5.3
-stderr 'go list -m: module rsc.io/quote: no matching versions for query ">v1.5.3"'
+stderr 'go: module rsc.io/quote: no matching versions for query ">v1.5.3"'
 
 go list -m -e -f '{{.Error.Err}}' rsc.io/quote@>v1.5.3
 stdout 'no matching versions for query ">v1.5.3"'
diff --git a/src/cmd/go/testdata/script/mod_query_empty.txt b/src/cmd/go/testdata/script/mod_query_empty.txt
index f8b6e3e..af08711 100644
--- a/src/cmd/go/testdata/script/mod_query_empty.txt
+++ b/src/cmd/go/testdata/script/mod_query_empty.txt
@@ -8,7 +8,7 @@
 env GOPROXY=file:///$WORK/badproxy
 cp go.mod.orig go.mod
 ! go get -d example.com/join/subpkg
-stderr 'go get: example.com/join/subpkg@v0.0.0-20190624000000-123456abcdef: .*'
+stderr 'go: example.com/join/subpkg@v0.0.0-20190624000000-123456abcdef: .*'
 
 # If @v/list is empty, the 'go' command should still try to resolve
 # other module paths.
@@ -40,7 +40,7 @@
 chmod 0000 $WORK/gatekeeper/example.com/join/subpkg/@latest
 cp go.mod.orig go.mod
 ! go get -d example.com/join/subpkg
-stderr 'go get: module example.com/join/subpkg: (invalid response from proxy ".+": invalid character .+|reading file://.*/gatekeeper/example.com/join/subpkg/@latest: .+)'
+stderr 'go: module example.com/join/subpkg: (invalid response from proxy ".+": invalid character .+|reading file://.*/gatekeeper/example.com/join/subpkg/@latest: .+)'
 
 -- go.mod.orig --
 module example.com/othermodule
diff --git a/src/cmd/go/testdata/script/mod_query_exclude.txt b/src/cmd/go/testdata/script/mod_query_exclude.txt
index b001969..8eae42d 100644
--- a/src/cmd/go/testdata/script/mod_query_exclude.txt
+++ b/src/cmd/go/testdata/script/mod_query_exclude.txt
@@ -19,7 +19,7 @@
 # get excluded version
 cp go.exclude.mod go.exclude.mod.orig
 ! go get -modfile=go.exclude.mod -d rsc.io/quote@v1.5.0
-stderr '^go get: rsc.io/quote@v1.5.0: excluded by go.mod$'
+stderr '^go: rsc.io/quote@v1.5.0: excluded by go.mod$'
 
 # get non-excluded version
 cp go.exclude.mod.orig go.exclude.mod
diff --git a/src/cmd/go/testdata/script/mod_query_main.txt b/src/cmd/go/testdata/script/mod_query_main.txt
index 39e5841..2a2fa42 100644
--- a/src/cmd/go/testdata/script/mod_query_main.txt
+++ b/src/cmd/go/testdata/script/mod_query_main.txt
@@ -6,9 +6,9 @@
 # 'go mod download' will not download @upgrade or @patch, since they always
 # resolve to the main module.
 go mod download rsc.io/quote@upgrade
-stderr '^go mod download: skipping argument rsc.io/quote@upgrade that resolves to the main module$'
+stderr '^go: skipping download of rsc.io/quote@upgrade that resolves to the main module$'
 go mod download rsc.io/quote@patch
-stderr '^go mod download: skipping argument rsc.io/quote@patch that resolves to the main module$'
+stderr '^go: skipping download of rsc.io/quote@patch that resolves to the main module$'
 
 # 'go list -m' can show a version of the main module.
 go list -m rsc.io/quote@5d9f230b
@@ -31,11 +31,11 @@
 # 'go get' will not attempt to upgrade the main module to any specific version.
 # See also: mod_get_main.txt.
 ! go get rsc.io/quote@5d9f230b
-stderr '^go get: can''t request version "5d9f230b" of the main module \(rsc.io/quote\)$'
+stderr '^go: can''t request version "5d9f230b" of the main module \(rsc.io/quote\)$'
 ! go get rsc.io/quote@v1.5.2
-stderr '^go get: can''t request version "v1.5.2" of the main module \(rsc.io/quote\)$'
+stderr '^go: can''t request version "v1.5.2" of the main module \(rsc.io/quote\)$'
 ! go get rsc.io/quote@latest
-stderr '^go get: can''t request version "latest" of the main module \(rsc.io/quote\)$'
+stderr '^go: can''t request version "latest" of the main module \(rsc.io/quote\)$'
 
 -- go.mod --
 module rsc.io/quote
diff --git a/src/cmd/go/testdata/script/mod_replace_gopkgin.txt b/src/cmd/go/testdata/script/mod_replace_gopkgin.txt
index d24f37b..df752d9 100644
--- a/src/cmd/go/testdata/script/mod_replace_gopkgin.txt
+++ b/src/cmd/go/testdata/script/mod_replace_gopkgin.txt
@@ -35,7 +35,7 @@
 # A mismatched gopkg.in path should not be able to replace a different major version.
 cd ../3-to-gomod-4
 ! go list -m gopkg.in/src-d/go-git.v3
-stderr '^go list -m: gopkg\.in/src-d/go-git\.v3@v3\.2\.0 \(replaced by gopkg\.in/src-d/go-git\.v3@v3\.0\.0-20190801152248-0d1a009cbb60\): version "v3\.0\.0-20190801152248-0d1a009cbb60" invalid: go\.mod has non-\.\.\.\.v3 module path "gopkg\.in/src-d/go-git\.v4" at revision 0d1a009cbb60$'
+stderr '^go: gopkg\.in/src-d/go-git\.v3@v3\.2\.0 \(replaced by gopkg\.in/src-d/go-git\.v3@v3\.0\.0-20190801152248-0d1a009cbb60\): version "v3\.0\.0-20190801152248-0d1a009cbb60" invalid: go\.mod has non-\.\.\.\.v3 module path "gopkg\.in/src-d/go-git\.v4" at revision 0d1a009cbb60$'
 
 -- 4-to-4/go.mod --
 module golang.org/issue/34254
diff --git a/src/cmd/go/testdata/script/mod_retract_fix_version.txt b/src/cmd/go/testdata/script/mod_retract_fix_version.txt
index e45758b..9ae49f5 100644
--- a/src/cmd/go/testdata/script/mod_retract_fix_version.txt
+++ b/src/cmd/go/testdata/script/mod_retract_fix_version.txt
@@ -15,7 +15,7 @@
 # If a retracted version doesn't match the module's major version suffx,
 # an error should be reported.
 ! go mod edit -retract=v3.0.1
-stderr '^go mod: -retract=v3.0.1: version "v3.0.1" invalid: should be v2, not v3$'
+stderr '^go: -retract=v3.0.1: version "v3.0.1" invalid: should be v2, not v3$'
 cp go.mod.mismatch-v2 go.mod
 ! go list -m all
 stderr 'go.mod:3: retract rsc.io/quote/v2: version "v3.0.1" invalid: should be v2, not v3$'
diff --git a/src/cmd/go/testdata/script/mod_retract_pseudo_base.txt b/src/cmd/go/testdata/script/mod_retract_pseudo_base.txt
index eb00e84..d1a5e12 100644
--- a/src/cmd/go/testdata/script/mod_retract_pseudo_base.txt
+++ b/src/cmd/go/testdata/script/mod_retract_pseudo_base.txt
@@ -29,7 +29,7 @@
 stdout '^vcs-test.golang.org/git/retract-pseudo.git v1.0.1-0.20201009173747-713affd19d7b$'
 
 ! go get -d vcs-test.golang.org/git/retract-pseudo.git@v1.0.1-0.20201009173747-64c061ed4371
-stderr '^go get: vcs-test.golang.org/git/retract-pseudo.git@v1.0.1-0.20201009173747-64c061ed4371: invalid pseudo-version: tag \(v1.0.0\) found on revision 64c061ed4371 is already canonical, so should not be replaced with a pseudo-version derived from that tag$'
+stderr '^go: vcs-test.golang.org/git/retract-pseudo.git@v1.0.1-0.20201009173747-64c061ed4371: invalid pseudo-version: tag \(v1.0.0\) found on revision 64c061ed4371 is already canonical, so should not be replaced with a pseudo-version derived from that tag$'
 
 -- retract-pseudo.sh --
 #!/bin/bash
diff --git a/src/cmd/go/testdata/script/mod_run_nonmain.txt b/src/cmd/go/testdata/script/mod_run_nonmain.txt
index 036755d..8435fc0 100644
--- a/src/cmd/go/testdata/script/mod_run_nonmain.txt
+++ b/src/cmd/go/testdata/script/mod_run_nonmain.txt
@@ -7,7 +7,7 @@
 
 ! go run ./...
 stderr '^go: warning: "\./\.\.\." matched only non-main packages$'
-stderr '^go run: no packages loaded from \./\.\.\.$'
+stderr '^go: no packages loaded from \./\.\.\.$'
 
 -- go.mod --
 module example.net/nonmain
diff --git a/src/cmd/go/testdata/script/mod_run_pkg_version.txt b/src/cmd/go/testdata/script/mod_run_pkg_version.txt
index e921fab..c3a218d 100644
--- a/src/cmd/go/testdata/script/mod_run_pkg_version.txt
+++ b/src/cmd/go/testdata/script/mod_run_pkg_version.txt
@@ -21,7 +21,7 @@
 cd m
 cp go.mod go.mod.orig
 ! go list -m all
-stderr '^go list -m: example.com/cmd@v1.1.0-doesnotexist: missing go.sum entry; to add it:\n\tgo mod download example.com/cmd$'
+stderr '^go: example.com/cmd@v1.1.0-doesnotexist: missing go.sum entry; to add it:\n\tgo mod download example.com/cmd$'
 go run example.com/cmd/a@v1.0.0
 stdout '^a@v1.0.0$'
 cmp go.mod go.mod.orig
@@ -92,12 +92,12 @@
 
 func main() {}
 -- replace-err --
-go run: example.com/cmd/a@v1.0.0-replace (in example.com/cmd@v1.0.0-replace):
+go: example.com/cmd/a@v1.0.0-replace (in example.com/cmd@v1.0.0-replace):
 	The go.mod file for the module providing named packages contains one or
 	more replace directives. It must not contain directives that would cause
 	it to be interpreted differently than if it were the main module.
 -- exclude-err --
-go run: example.com/cmd/a@v1.0.0-exclude (in example.com/cmd@v1.0.0-exclude):
+go: example.com/cmd/a@v1.0.0-exclude (in example.com/cmd@v1.0.0-exclude):
 	The go.mod file for the module providing named packages contains one or
 	more exclude directives. It must not contain directives that would cause
 	it to be interpreted differently than if it were the main module.
diff --git a/src/cmd/go/testdata/script/mod_sum_readonly.txt b/src/cmd/go/testdata/script/mod_sum_readonly.txt
index 113f13e..57c5bbe 100644
--- a/src/cmd/go/testdata/script/mod_sum_readonly.txt
+++ b/src/cmd/go/testdata/script/mod_sum_readonly.txt
@@ -4,7 +4,7 @@
 # When a sum is needed to load the build list, we get an error for the
 # specific module. The .mod file is not downloaded, and go.sum is not written.
 ! go list -m all
-stderr '^go list -m: rsc.io/quote@v1.5.2: missing go.sum entry; to add it:\n\tgo mod download rsc.io/quote$'
+stderr '^go: rsc.io/quote@v1.5.2: missing go.sum entry; to add it:\n\tgo mod download rsc.io/quote$'
 ! exists $GOPATH/pkg/mod/cache/download/rsc.io/quote/@v/v1.5.2.mod
 ! exists go.sum
 
@@ -12,7 +12,7 @@
 # we should see the same error.
 cp go.sum.h2only go.sum
 ! go list -m all
-stderr '^go list -m: rsc.io/quote@v1.5.2: missing go.sum entry; to add it:\n\tgo mod download rsc.io/quote$'
+stderr '^go: rsc.io/quote@v1.5.2: missing go.sum entry; to add it:\n\tgo mod download rsc.io/quote$'
 ! exists $GOPATH/pkg/mod/cache/download/rsc.io/quote/@v/v1.5.2.mod
 cmp go.sum go.sum.h2only
 rm go.sum
@@ -21,7 +21,7 @@
 cp go.mod go.mod.orig
 go mod edit -replace rsc.io/quote@v1.5.2=rsc.io/quote@v1.5.1
 ! go list -m all
-stderr '^go list -m: rsc.io/quote@v1.5.2 \(replaced by rsc.io/quote@v1.5.1\): missing go.sum entry; to add it:\n\tgo mod download rsc.io/quote$'
+stderr '^go: rsc.io/quote@v1.5.2 \(replaced by rsc.io/quote@v1.5.1\): missing go.sum entry; to add it:\n\tgo mod download rsc.io/quote$'
 ! exists $GOPATH/pkg/mod/cache/download/rsc.io/quote/@v/v1.5.1.mod
 ! exists go.sum
 cp go.mod.orig go.mod
diff --git a/src/cmd/go/testdata/script/mod_sumdb.txt b/src/cmd/go/testdata/script/mod_sumdb.txt
index fa3483c..dd791be 100644
--- a/src/cmd/go/testdata/script/mod_sumdb.txt
+++ b/src/cmd/go/testdata/script/mod_sumdb.txt
@@ -9,7 +9,7 @@
 cp go.mod.orig go.mod
 env GOSUMDB=$sumdb' '$proxy/sumdb-wrong
 ! go get -d rsc.io/quote
-stderr 'go get: rsc.io/quote@v1.5.2: verifying module: checksum mismatch'
+stderr 'go: rsc.io/quote@v1.5.2: verifying module: checksum mismatch'
 stderr 'downloaded: h1:3fEy'
 stderr 'localhost.localdev/sumdb: h1:wrong'
 stderr 'SECURITY ERROR\nThis download does NOT match the one reported by the checksum server.'
diff --git a/src/cmd/go/testdata/script/mod_sumdb_file_path.txt b/src/cmd/go/testdata/script/mod_sumdb_file_path.txt
index 22fcbf3..575c7c4 100644
--- a/src/cmd/go/testdata/script/mod_sumdb_file_path.txt
+++ b/src/cmd/go/testdata/script/mod_sumdb_file_path.txt
@@ -13,7 +13,7 @@
 [windows] env GOPROXY=file:///$WORK/sumproxy,https://proxy.golang.org
 [!windows] env GOPROXY=file://$WORK/sumproxy,https://proxy.golang.org
 ! go get -d golang.org/x/text@v0.3.2
-stderr '^go get: golang.org/x/text@v0.3.2: verifying module: golang.org/x/text@v0.3.2: reading file://.*/sumdb/sum.golang.org/lookup/golang.org/x/text@v0.3.2: (no such file or directory|.*cannot find the path specified.*)'
+stderr '^go: golang.org/x/text@v0.3.2: verifying module: golang.org/x/text@v0.3.2: reading file://.*/sumdb/sum.golang.org/lookup/golang.org/x/text@v0.3.2: (no such file or directory|.*cannot find the path specified.*)'
 
 # If the proxy does not claim to support the database,
 # checksum verification should fall through to the next proxy,
diff --git a/src/cmd/go/testdata/script/mod_tidy_compat.txt b/src/cmd/go/testdata/script/mod_tidy_compat.txt
index 29cae17..18b297d 100644
--- a/src/cmd/go/testdata/script/mod_tidy_compat.txt
+++ b/src/cmd/go/testdata/script/mod_tidy_compat.txt
@@ -50,7 +50,7 @@
 
 go mod edit -go=1.16
 ! go list -m all
-stderr '^go list -m: example.net/lazy@v0.1.0 requires\n\texample.com/version@v1.0.1: missing go.sum entry; to add it:\n\tgo mod download example.com/version$'
+stderr '^go: example.net/lazy@v0.1.0 requires\n\texample.com/version@v1.0.1: missing go.sum entry; to add it:\n\tgo mod download example.com/version$'
 
 
 -- go.mod --
diff --git a/src/cmd/go/testdata/script/mod_tidy_compat_ambiguous.txt b/src/cmd/go/testdata/script/mod_tidy_compat_ambiguous.txt
index c544cb7..44bc58c 100644
--- a/src/cmd/go/testdata/script/mod_tidy_compat_ambiguous.txt
+++ b/src/cmd/go/testdata/script/mod_tidy_compat_ambiguous.txt
@@ -62,7 +62,7 @@
 
 go mod edit -go=1.16
 ! go list -m all
-stderr '^go list -m: example\.net/indirect@v0\.1\.0 requires\n\texample\.net/ambiguous@v0\.1\.0: missing go\.sum entry; to add it:\n\tgo mod download example\.net/ambiguous\n'
+stderr '^go: example\.net/indirect@v0\.1\.0 requires\n\texample\.net/ambiguous@v0\.1\.0: missing go\.sum entry; to add it:\n\tgo mod download example\.net/ambiguous\n'
 
 
 -- go.mod --
diff --git a/src/cmd/go/testdata/script/mod_tidy_too_new.txt b/src/cmd/go/testdata/script/mod_tidy_too_new.txt
index b9c53b5..8c34a99 100644
--- a/src/cmd/go/testdata/script/mod_tidy_too_new.txt
+++ b/src/cmd/go/testdata/script/mod_tidy_too_new.txt
@@ -9,7 +9,7 @@
 # would look like.
 
 ! go mod tidy
-stderr 'go mod tidy: go.mod file indicates go 2000.0, but maximum supported version is '$goversion'$'
+stderr 'go: go.mod file indicates go 2000.0, but maximum version supported by tidy is '$goversion'$'
 cmp go.mod go.mod.orig
 
 
@@ -18,7 +18,7 @@
 
 cp go.mod.orig go.mod
 go mod tidy -e
-stderr 'go mod tidy: go.mod file indicates go 2000.0, but maximum supported version is '$goversion'$'
+stderr 'go: go.mod file indicates go 2000.0, but maximum version supported by tidy is '$goversion'$'
 cmp go.mod go.mod.tidy
 
 
diff --git a/src/cmd/go/testdata/script/mod_upgrade_patch.txt b/src/cmd/go/testdata/script/mod_upgrade_patch.txt
index 8b34f8b..b8c178c 100644
--- a/src/cmd/go/testdata/script/mod_upgrade_patch.txt
+++ b/src/cmd/go/testdata/script/mod_upgrade_patch.txt
@@ -11,7 +11,7 @@
 
 # @patch should be rejected for modules not already in the build list.
 ! go get -d patch.example.com/depofdirectpatch@patch
-stderr '^go get: can''t query version "patch" of module patch.example.com/depofdirectpatch: no existing version is required$'
+stderr '^go: can''t query version "patch" of module patch.example.com/depofdirectpatch: no existing version is required$'
 cmp go.mod.orig go.mod
 
 # get -u=patch, with no arguments, should patch-update all dependencies
@@ -38,7 +38,7 @@
 go mod edit -droprequire=patch.example.com/direct
 cp go.mod go.mod.dropped
 ! go get -d all@patch
-stderr '^go get all@patch: can''t query version "patch" of module patch.example.com/direct: no existing version is required$'
+stderr '^go: all@patch: can''t query version "patch" of module patch.example.com/direct: no existing version is required$'
 cmp go.mod.dropped go.mod
 
 # Requesting the direct dependency with -u=patch but without an explicit version
@@ -86,7 +86,7 @@
 # Standard library packages cannot be upgraded explicitly.
 cp go.mod.orig go.mod
 ! go get cmd/vet@patch
-stderr 'go get: can''t request explicit version "patch" of standard library package cmd/vet$'
+stderr 'go: can''t request explicit version "patch" of standard library package cmd/vet$'
 
 # However, standard-library packages without explicit versions are fine.
 go get -d -u=patch -d cmd/go
diff --git a/src/cmd/go/testdata/script/mod_vendor.txt b/src/cmd/go/testdata/script/mod_vendor.txt
index 2622916..4eb80c2 100644
--- a/src/cmd/go/testdata/script/mod_vendor.txt
+++ b/src/cmd/go/testdata/script/mod_vendor.txt
@@ -40,15 +40,15 @@
 
 # -mod=vendor should cause 'go list' flags that look up versions to fail.
 ! go list -mod=vendor -versions -m x
-stderr '^go list -m: can''t determine available versions using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)$'
+stderr '^go: can''t determine available versions using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)$'
 ! go list -mod=vendor -u -m x
-stderr '^go list -m: can''t determine available upgrades using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)$'
+stderr '^go: can''t determine available upgrades using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)$'
 
 # 'go list -mod=vendor -m' on a transitive dependency that does not
 # provide vendored packages should give a helpful error rather than
 # 'not a known dependency'.
 ! go list -mod=vendor -f '{{.Version}} {{.Dir}}' -m diamondright
-stderr 'go list -m: module diamondright: can''t resolve module using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)'
+stderr 'go: module diamondright: can''t resolve module using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)'
 
 # 'go list -mod=mod' should report packages outside the import graph,
 # but 'go list -mod=vendor' should error out for them.
diff --git a/src/cmd/go/testdata/script/mod_vendor_auto.txt b/src/cmd/go/testdata/script/mod_vendor_auto.txt
index b0ea907..96db5c1 100644
--- a/src/cmd/go/testdata/script/mod_vendor_auto.txt
+++ b/src/cmd/go/testdata/script/mod_vendor_auto.txt
@@ -17,10 +17,10 @@
 stdout '^'$WORK'[/\\]auto[/\\]vendor[/\\]example.com[/\\]version$'
 
 ! go list -m all
-stderr 'go list -m: can''t compute ''all'' using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)'
+stderr 'go: can''t compute ''all'' using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)'
 
 ! go list -m -f '{{.Dir}}' all
-stderr 'go list -m: can''t compute ''all'' using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)'
+stderr 'go: can''t compute ''all'' using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)'
 
 # An explicit -mod=mod should force the vendor directory to be ignored.
 env GOFLAGS=-mod=mod
@@ -105,10 +105,10 @@
 # ...but 'go list -m' should continue to fail, this time without
 # referring to a -mod default that the user didn't set.
 ! go list -m all
-stderr 'go list -m: can''t compute ''all'' using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)'
+stderr 'go: can''t compute ''all'' using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)'
 
 ! go list -m -f '{{.Dir}}' all
-stderr 'go list -m: can''t compute ''all'' using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)'
+stderr 'go: can''t compute ''all'' using the vendor directory\n\t\(Use -mod=mod or -mod=readonly to bypass.\)'
 
 
 # 'go mod init' should work if there is already a GOPATH-mode vendor directory
diff --git a/src/cmd/go/testdata/script/mod_vendor_embed.txt b/src/cmd/go/testdata/script/mod_vendor_embed.txt
index be11415..b14fd99 100644
--- a/src/cmd/go/testdata/script/mod_vendor_embed.txt
+++ b/src/cmd/go/testdata/script/mod_vendor_embed.txt
@@ -6,11 +6,11 @@
 
 cd broken_no_matching_files
 ! go mod vendor
-stderr 'go mod vendor: pattern foo.txt: no matching files found'
+stderr 'go: pattern foo.txt: no matching files found'
 
 cd ../broken_bad_pattern
 ! go mod vendor
-stderr 'go mod vendor: pattern ../foo.txt: invalid pattern syntax'
+stderr 'go: pattern ../foo.txt: invalid pattern syntax'
 
 # matchPotentialSourceFile prunes out tests and unbuilt code.
 # Make sure that they are vendored if they are embedded files.
diff --git a/src/cmd/go/testdata/script/run_wildcard.txt b/src/cmd/go/testdata/script/run_wildcard.txt
index 72036d1..3e7e7b7 100644
--- a/src/cmd/go/testdata/script/run_wildcard.txt
+++ b/src/cmd/go/testdata/script/run_wildcard.txt
@@ -4,4 +4,4 @@
 # go run x/... should not panic when directory x doesn't exist.
 
 ! go run nonexistent/...
-stderr '^go run: no packages loaded from nonexistent/...$'
+stderr '^go: no packages loaded from nonexistent/...$'
diff --git a/src/cmd/go/testdata/script/test_flag.txt b/src/cmd/go/testdata/script/test_flag.txt
index 0142b3f..d168cfe 100644
--- a/src/cmd/go/testdata/script/test_flag.txt
+++ b/src/cmd/go/testdata/script/test_flag.txt
@@ -9,13 +9,13 @@
 # However, it should be an error to use custom flags when -i or -c are used,
 # since we know for sure that no test binary will run at all.
 ! go test -i -custom
-stderr '^go test: unknown flag -custom cannot be used with -i$'
+stderr '^go: unknown flag -custom cannot be used with -i$'
 ! go test -c -custom
-stderr '^go test: unknown flag -custom cannot be used with -c$'
+stderr '^go: unknown flag -custom cannot be used with -c$'
 
 # The same should apply even if -c or -i come after a custom flag.
 ! go test -custom -c
-stderr '^go test: unknown flag -custom cannot be used with -c$'
+stderr '^go: unknown flag -custom cannot be used with -c$'
 
 -- go.mod --
 module m
diff --git a/src/cmd/go/testdata/script/test_race_install.txt b/src/cmd/go/testdata/script/test_race_install.txt
index 8b1f343..a1d47a7 100644
--- a/src/cmd/go/testdata/script/test_race_install.txt
+++ b/src/cmd/go/testdata/script/test_race_install.txt
@@ -15,4 +15,4 @@
 -- pkg/pkg.go --
 package p
 -- stderr.txt --
-go test: -i flag is deprecated
+go: -i flag is deprecated