cmd/go: use verbose flag to log proxy activities

Fixes #29515
Fixes #30604

Change-Id: Ie75a331cd6ca51806c5720443506d4fe0bec28cf
Reviewed-on: https://go-review.googlesource.com/c/go/+/227162
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
diff --git a/src/cmd/go/proxy_test.go b/src/cmd/go/proxy_test.go
index 7f58fb8..42972f5 100644
--- a/src/cmd/go/proxy_test.go
+++ b/src/cmd/go/proxy_test.go
@@ -91,7 +91,7 @@
 		encPath := strings.ReplaceAll(name[:i], "_", "/")
 		path, err := module.UnescapePath(encPath)
 		if err != nil {
-			if encPath != "example.com/invalidpath/v1" {
+			if testing.Verbose() && encPath != "example.com/invalidpath/v1" {
 				fmt.Fprintf(os.Stderr, "go proxy_test: %v\n", err)
 			}
 			continue
@@ -137,13 +137,6 @@
 		return
 	}
 
-	// /mod/quiet/ does not print errors.
-	quiet := false
-	if strings.HasPrefix(path, "quiet/") {
-		path = path[len("quiet/"):]
-		quiet = true
-	}
-
 	// Next element may opt into special behavior.
 	if j := strings.Index(path, "/"); j >= 0 {
 		n, err := strconv.Atoi(path[:j])
@@ -220,7 +213,7 @@
 		enc := path[:i]
 		modPath, err := module.UnescapePath(enc)
 		if err != nil {
-			if !quiet {
+			if testing.Verbose() {
 				fmt.Fprintf(os.Stderr, "go proxy_test: %v\n", err)
 			}
 			http.NotFound(w, r)
@@ -273,7 +266,7 @@
 	enc, file := path[:i], path[i+len("/@v/"):]
 	path, err := module.UnescapePath(enc)
 	if err != nil {
-		if !quiet {
+		if testing.Verbose() {
 			fmt.Fprintf(os.Stderr, "go proxy_test: %v\n", err)
 		}
 		http.NotFound(w, r)
@@ -339,7 +332,7 @@
 
 	a, err := readArchive(path, vers)
 	if err != nil {
-		if !quiet {
+		if testing.Verbose() {
 			fmt.Fprintf(os.Stderr, "go proxy: no archive %s %s: %v\n", path, vers, err)
 		}
 		if errors.Is(err, os.ErrNotExist) {
@@ -393,7 +386,7 @@
 		}).(cached)
 
 		if c.err != nil {
-			if !quiet {
+			if testing.Verbose() {
 				fmt.Fprintf(os.Stderr, "go proxy: %v\n", c.err)
 			}
 			http.Error(w, c.err.Error(), 500)
diff --git a/src/cmd/go/testdata/script/mod_download.txt b/src/cmd/go/testdata/script/mod_download.txt
index 3573928..bb5c462 100644
--- a/src/cmd/go/testdata/script/mod_download.txt
+++ b/src/cmd/go/testdata/script/mod_download.txt
@@ -1,5 +1,4 @@
 env GO111MODULE=on
-env GOPROXY=$GOPROXY/quiet
 
 # download with version should print nothing
 go mod download rsc.io/quote@v1.5.0
diff --git a/src/cmd/go/testdata/script/mod_download_json.txt b/src/cmd/go/testdata/script/mod_download_json.txt
index 01c35dd..2629168 100644
--- a/src/cmd/go/testdata/script/mod_download_json.txt
+++ b/src/cmd/go/testdata/script/mod_download_json.txt
@@ -1,5 +1,4 @@
 env GO111MODULE=on
-env GOPROXY=$GOPROXY/quiet
 env GOSUMDB=$sumdb' '$proxy/sumdb-wrong
 
 # download -json with version should print JSON on sumdb failure
diff --git a/src/cmd/go/testdata/script/mod_get_commit.txt b/src/cmd/go/testdata/script/mod_get_commit.txt
index d108242..857740a 100644
--- a/src/cmd/go/testdata/script/mod_get_commit.txt
+++ b/src/cmd/go/testdata/script/mod_get_commit.txt
@@ -1,5 +1,4 @@
 env GO111MODULE=on
-env GOPROXY=$GOPROXY/quiet
 [short] skip
 
 # @commit should resolve
diff --git a/src/cmd/go/testdata/script/mod_get_moved.txt b/src/cmd/go/testdata/script/mod_get_moved.txt
index edc41cf..b46ec8e 100644
--- a/src/cmd/go/testdata/script/mod_get_moved.txt
+++ b/src/cmd/go/testdata/script/mod_get_moved.txt
@@ -1,5 +1,4 @@
 env GO111MODULE=on
-env GOPROXY=$GOPROXY/quiet
 [short] skip
 
 # A 'go get' that worked at a previous version should continue to work at that version,
diff --git a/src/cmd/go/testdata/script/mod_query_exclude.txt b/src/cmd/go/testdata/script/mod_query_exclude.txt
index 1ae0d17..a64a8e1 100644
--- a/src/cmd/go/testdata/script/mod_query_exclude.txt
+++ b/src/cmd/go/testdata/script/mod_query_exclude.txt
@@ -1,5 +1,4 @@
 env GO111MODULE=on
-env GOPROXY=$GOPROXY/quiet
 
 # get excluded version
 cp go.mod1 go.mod