diff --git a/src/archive/tar/common.go b/src/archive/tar/common.go
index dee9e47..c667cfc 100644
--- a/src/archive/tar/common.go
+++ b/src/archive/tar/common.go
@@ -13,8 +13,8 @@
 import (
 	"errors"
 	"fmt"
+	"io/fs"
 	"math"
-	"os"
 	"path"
 	"reflect"
 	"strconv"
@@ -525,12 +525,12 @@
 	return format, paxHdrs, err
 }
 
-// FileInfo returns an os.FileInfo for the Header.
-func (h *Header) FileInfo() os.FileInfo {
+// FileInfo returns an fs.FileInfo for the Header.
+func (h *Header) FileInfo() fs.FileInfo {
 	return headerFileInfo{h}
 }
 
-// headerFileInfo implements os.FileInfo.
+// headerFileInfo implements fs.FileInfo.
 type headerFileInfo struct {
 	h *Header
 }
@@ -549,57 +549,57 @@
 }
 
 // Mode returns the permission and mode bits for the headerFileInfo.
-func (fi headerFileInfo) Mode() (mode os.FileMode) {
+func (fi headerFileInfo) Mode() (mode fs.FileMode) {
 	// Set file permission bits.
-	mode = os.FileMode(fi.h.Mode).Perm()
+	mode = fs.FileMode(fi.h.Mode).Perm()
 
 	// Set setuid, setgid and sticky bits.
 	if fi.h.Mode&c_ISUID != 0 {
-		mode |= os.ModeSetuid
+		mode |= fs.ModeSetuid
 	}
 	if fi.h.Mode&c_ISGID != 0 {
-		mode |= os.ModeSetgid
+		mode |= fs.ModeSetgid
 	}
 	if fi.h.Mode&c_ISVTX != 0 {
-		mode |= os.ModeSticky
+		mode |= fs.ModeSticky
 	}
 
 	// Set file mode bits; clear perm, setuid, setgid, and sticky bits.
-	switch m := os.FileMode(fi.h.Mode) &^ 07777; m {
+	switch m := fs.FileMode(fi.h.Mode) &^ 07777; m {
 	case c_ISDIR:
-		mode |= os.ModeDir
+		mode |= fs.ModeDir
 	case c_ISFIFO:
-		mode |= os.ModeNamedPipe
+		mode |= fs.ModeNamedPipe
 	case c_ISLNK:
-		mode |= os.ModeSymlink
+		mode |= fs.ModeSymlink
 	case c_ISBLK:
-		mode |= os.ModeDevice
+		mode |= fs.ModeDevice
 	case c_ISCHR:
-		mode |= os.ModeDevice
-		mode |= os.ModeCharDevice
+		mode |= fs.ModeDevice
+		mode |= fs.ModeCharDevice
 	case c_ISSOCK:
-		mode |= os.ModeSocket
+		mode |= fs.ModeSocket
 	}
 
 	switch fi.h.Typeflag {
 	case TypeSymlink:
-		mode |= os.ModeSymlink
+		mode |= fs.ModeSymlink
 	case TypeChar:
-		mode |= os.ModeDevice
-		mode |= os.ModeCharDevice
+		mode |= fs.ModeDevice
+		mode |= fs.ModeCharDevice
 	case TypeBlock:
-		mode |= os.ModeDevice
+		mode |= fs.ModeDevice
 	case TypeDir:
-		mode |= os.ModeDir
+		mode |= fs.ModeDir
 	case TypeFifo:
-		mode |= os.ModeNamedPipe
+		mode |= fs.ModeNamedPipe
 	}
 
 	return mode
 }
 
 // sysStat, if non-nil, populates h from system-dependent fields of fi.
-var sysStat func(fi os.FileInfo, h *Header) error
+var sysStat func(fi fs.FileInfo, h *Header) error
 
 const (
 	// Mode constants from the USTAR spec:
@@ -623,10 +623,10 @@
 // If fi describes a symlink, FileInfoHeader records link as the link target.
 // If fi describes a directory, a slash is appended to the name.
 //
-// Since os.FileInfo's Name method only returns the base name of
+// Since fs.FileInfo's Name method only returns the base name of
 // the file it describes, it may be necessary to modify Header.Name
 // to provide the full path name of the file.
-func FileInfoHeader(fi os.FileInfo, link string) (*Header, error) {
+func FileInfoHeader(fi fs.FileInfo, link string) (*Header, error) {
 	if fi == nil {
 		return nil, errors.New("archive/tar: FileInfo is nil")
 	}
@@ -643,29 +643,29 @@
 	case fi.IsDir():
 		h.Typeflag = TypeDir
 		h.Name += "/"
-	case fm&os.ModeSymlink != 0:
+	case fm&fs.ModeSymlink != 0:
 		h.Typeflag = TypeSymlink
 		h.Linkname = link
-	case fm&os.ModeDevice != 0:
-		if fm&os.ModeCharDevice != 0 {
+	case fm&fs.ModeDevice != 0:
+		if fm&fs.ModeCharDevice != 0 {
 			h.Typeflag = TypeChar
 		} else {
 			h.Typeflag = TypeBlock
 		}
-	case fm&os.ModeNamedPipe != 0:
+	case fm&fs.ModeNamedPipe != 0:
 		h.Typeflag = TypeFifo
-	case fm&os.ModeSocket != 0:
+	case fm&fs.ModeSocket != 0:
 		return nil, fmt.Errorf("archive/tar: sockets not supported")
 	default:
 		return nil, fmt.Errorf("archive/tar: unknown file mode %v", fm)
 	}
-	if fm&os.ModeSetuid != 0 {
+	if fm&fs.ModeSetuid != 0 {
 		h.Mode |= c_ISUID
 	}
-	if fm&os.ModeSetgid != 0 {
+	if fm&fs.ModeSetgid != 0 {
 		h.Mode |= c_ISGID
 	}
-	if fm&os.ModeSticky != 0 {
+	if fm&fs.ModeSticky != 0 {
 		h.Mode |= c_ISVTX
 	}
 	// If possible, populate additional fields from OS-specific
diff --git a/src/archive/tar/stat_unix.go b/src/archive/tar/stat_unix.go
index 8df3616..581d87d 100644
--- a/src/archive/tar/stat_unix.go
+++ b/src/archive/tar/stat_unix.go
@@ -7,7 +7,7 @@
 package tar
 
 import (
-	"os"
+	"io/fs"
 	"os/user"
 	"runtime"
 	"strconv"
@@ -23,7 +23,7 @@
 // The downside is that renaming uname or gname by the OS never takes effect.
 var userMap, groupMap sync.Map // map[int]string
 
-func statUnix(fi os.FileInfo, h *Header) error {
+func statUnix(fi fs.FileInfo, h *Header) error {
 	sys, ok := fi.Sys().(*syscall.Stat_t)
 	if !ok {
 		return nil
diff --git a/src/archive/tar/tar_test.go b/src/archive/tar/tar_test.go
index 2676853..f605dae 100644
--- a/src/archive/tar/tar_test.go
+++ b/src/archive/tar/tar_test.go
@@ -10,6 +10,7 @@
 	"fmt"
 	"internal/testenv"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"math"
 	"os"
@@ -338,7 +339,7 @@
 
 type headerRoundTripTest struct {
 	h  *Header
-	fm os.FileMode
+	fm fs.FileMode
 }
 
 func TestHeaderRoundTrip(t *testing.T) {
@@ -361,7 +362,7 @@
 			ModTime:  time.Unix(1360600852, 0),
 			Typeflag: TypeSymlink,
 		},
-		fm: 0777 | os.ModeSymlink,
+		fm: 0777 | fs.ModeSymlink,
 	}, {
 		// character device node.
 		h: &Header{
@@ -371,7 +372,7 @@
 			ModTime:  time.Unix(1360578951, 0),
 			Typeflag: TypeChar,
 		},
-		fm: 0666 | os.ModeDevice | os.ModeCharDevice,
+		fm: 0666 | fs.ModeDevice | fs.ModeCharDevice,
 	}, {
 		// block device node.
 		h: &Header{
@@ -381,7 +382,7 @@
 			ModTime:  time.Unix(1360578954, 0),
 			Typeflag: TypeBlock,
 		},
-		fm: 0660 | os.ModeDevice,
+		fm: 0660 | fs.ModeDevice,
 	}, {
 		// directory.
 		h: &Header{
@@ -391,7 +392,7 @@
 			ModTime:  time.Unix(1360601116, 0),
 			Typeflag: TypeDir,
 		},
-		fm: 0755 | os.ModeDir,
+		fm: 0755 | fs.ModeDir,
 	}, {
 		// fifo node.
 		h: &Header{
@@ -401,7 +402,7 @@
 			ModTime:  time.Unix(1360578949, 0),
 			Typeflag: TypeFifo,
 		},
-		fm: 0600 | os.ModeNamedPipe,
+		fm: 0600 | fs.ModeNamedPipe,
 	}, {
 		// setuid.
 		h: &Header{
@@ -411,7 +412,7 @@
 			ModTime:  time.Unix(1355405093, 0),
 			Typeflag: TypeReg,
 		},
-		fm: 0755 | os.ModeSetuid,
+		fm: 0755 | fs.ModeSetuid,
 	}, {
 		// setguid.
 		h: &Header{
@@ -421,7 +422,7 @@
 			ModTime:  time.Unix(1360602346, 0),
 			Typeflag: TypeReg,
 		},
-		fm: 0750 | os.ModeSetgid,
+		fm: 0750 | fs.ModeSetgid,
 	}, {
 		// sticky.
 		h: &Header{
@@ -431,7 +432,7 @@
 			ModTime:  time.Unix(1360602540, 0),
 			Typeflag: TypeReg,
 		},
-		fm: 0600 | os.ModeSticky,
+		fm: 0600 | fs.ModeSticky,
 	}, {
 		// hard link.
 		h: &Header{
diff --git a/src/archive/zip/reader_test.go b/src/archive/zip/reader_test.go
index adca87a..8a32d9c 100644
--- a/src/archive/zip/reader_test.go
+++ b/src/archive/zip/reader_test.go
@@ -10,6 +10,7 @@
 	"encoding/hex"
 	"internal/obscuretestdata"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -30,7 +31,7 @@
 
 type ZipTestFile struct {
 	Name     string
-	Mode     os.FileMode
+	Mode     fs.FileMode
 	NonUTF8  bool
 	ModTime  time.Time
 	Modified time.Time
@@ -107,7 +108,7 @@
 				Name:     "symlink",
 				Content:  []byte("../target"),
 				Modified: time.Date(2012, 2, 3, 19, 56, 48, 0, timeZone(-2*time.Hour)),
-				Mode:     0777 | os.ModeSymlink,
+				Mode:     0777 | fs.ModeSymlink,
 			},
 		},
 	},
@@ -149,7 +150,7 @@
 				Name:     "dir/empty/",
 				Content:  []byte{},
 				Modified: time.Date(2011, 12, 8, 10, 8, 6, 0, time.UTC),
-				Mode:     os.ModeDir | 0777,
+				Mode:     fs.ModeDir | 0777,
 			},
 			{
 				Name:     "readonly",
@@ -179,7 +180,7 @@
 				Name:     "dir/empty/",
 				Content:  []byte{},
 				Modified: time.Date(2011, 12, 8, 10, 8, 6, 0, timeZone(0)),
-				Mode:     os.ModeDir | 0777,
+				Mode:     fs.ModeDir | 0777,
 			},
 			{
 				Name:     "readonly",
@@ -645,7 +646,7 @@
 	}
 }
 
-func testFileMode(t *testing.T, f *File, want os.FileMode) {
+func testFileMode(t *testing.T, f *File, want fs.FileMode) {
 	mode := f.Mode()
 	if want == 0 {
 		t.Errorf("%s mode: got %v, want none", f.Name, mode)
diff --git a/src/archive/zip/struct.go b/src/archive/zip/struct.go
index 686e797..355c570 100644
--- a/src/archive/zip/struct.go
+++ b/src/archive/zip/struct.go
@@ -20,7 +20,7 @@
 package zip
 
 import (
-	"os"
+	"io/fs"
 	"path"
 	"time"
 )
@@ -137,12 +137,12 @@
 	ExternalAttrs      uint32 // Meaning depends on CreatorVersion
 }
 
-// FileInfo returns an os.FileInfo for the FileHeader.
-func (h *FileHeader) FileInfo() os.FileInfo {
+// FileInfo returns an fs.FileInfo for the FileHeader.
+func (h *FileHeader) FileInfo() fs.FileInfo {
 	return headerFileInfo{h}
 }
 
-// headerFileInfo implements os.FileInfo.
+// headerFileInfo implements fs.FileInfo.
 type headerFileInfo struct {
 	fh *FileHeader
 }
@@ -161,17 +161,17 @@
 	}
 	return fi.fh.Modified.UTC()
 }
-func (fi headerFileInfo) Mode() os.FileMode { return fi.fh.Mode() }
+func (fi headerFileInfo) Mode() fs.FileMode { return fi.fh.Mode() }
 func (fi headerFileInfo) Sys() interface{}  { return fi.fh }
 
 // FileInfoHeader creates a partially-populated FileHeader from an
-// os.FileInfo.
-// Because os.FileInfo's Name method returns only the base name of
+// fs.FileInfo.
+// Because fs.FileInfo's Name method returns only the base name of
 // the file it describes, it may be necessary to modify the Name field
 // of the returned header to provide the full path name of the file.
 // If compression is desired, callers should set the FileHeader.Method
 // field; it is unset by default.
-func FileInfoHeader(fi os.FileInfo) (*FileHeader, error) {
+func FileInfoHeader(fi fs.FileInfo) (*FileHeader, error) {
 	size := fi.Size()
 	fh := &FileHeader{
 		Name:               fi.Name(),
@@ -280,7 +280,7 @@
 )
 
 // Mode returns the permission and mode bits for the FileHeader.
-func (h *FileHeader) Mode() (mode os.FileMode) {
+func (h *FileHeader) Mode() (mode fs.FileMode) {
 	switch h.CreatorVersion >> 8 {
 	case creatorUnix, creatorMacOSX:
 		mode = unixModeToFileMode(h.ExternalAttrs >> 16)
@@ -288,18 +288,18 @@
 		mode = msdosModeToFileMode(h.ExternalAttrs)
 	}
 	if len(h.Name) > 0 && h.Name[len(h.Name)-1] == '/' {
-		mode |= os.ModeDir
+		mode |= fs.ModeDir
 	}
 	return mode
 }
 
 // SetMode changes the permission and mode bits for the FileHeader.
-func (h *FileHeader) SetMode(mode os.FileMode) {
+func (h *FileHeader) SetMode(mode fs.FileMode) {
 	h.CreatorVersion = h.CreatorVersion&0xff | creatorUnix<<8
 	h.ExternalAttrs = fileModeToUnixMode(mode) << 16
 
 	// set MSDOS attributes too, as the original zip does.
-	if mode&os.ModeDir != 0 {
+	if mode&fs.ModeDir != 0 {
 		h.ExternalAttrs |= msdosDir
 	}
 	if mode&0200 == 0 {
@@ -312,9 +312,9 @@
 	return h.CompressedSize64 >= uint32max || h.UncompressedSize64 >= uint32max
 }
 
-func msdosModeToFileMode(m uint32) (mode os.FileMode) {
+func msdosModeToFileMode(m uint32) (mode fs.FileMode) {
 	if m&msdosDir != 0 {
-		mode = os.ModeDir | 0777
+		mode = fs.ModeDir | 0777
 	} else {
 		mode = 0666
 	}
@@ -324,64 +324,64 @@
 	return mode
 }
 
-func fileModeToUnixMode(mode os.FileMode) uint32 {
+func fileModeToUnixMode(mode fs.FileMode) uint32 {
 	var m uint32
-	switch mode & os.ModeType {
+	switch mode & fs.ModeType {
 	default:
 		m = s_IFREG
-	case os.ModeDir:
+	case fs.ModeDir:
 		m = s_IFDIR
-	case os.ModeSymlink:
+	case fs.ModeSymlink:
 		m = s_IFLNK
-	case os.ModeNamedPipe:
+	case fs.ModeNamedPipe:
 		m = s_IFIFO
-	case os.ModeSocket:
+	case fs.ModeSocket:
 		m = s_IFSOCK
-	case os.ModeDevice:
-		if mode&os.ModeCharDevice != 0 {
+	case fs.ModeDevice:
+		if mode&fs.ModeCharDevice != 0 {
 			m = s_IFCHR
 		} else {
 			m = s_IFBLK
 		}
 	}
-	if mode&os.ModeSetuid != 0 {
+	if mode&fs.ModeSetuid != 0 {
 		m |= s_ISUID
 	}
-	if mode&os.ModeSetgid != 0 {
+	if mode&fs.ModeSetgid != 0 {
 		m |= s_ISGID
 	}
-	if mode&os.ModeSticky != 0 {
+	if mode&fs.ModeSticky != 0 {
 		m |= s_ISVTX
 	}
 	return m | uint32(mode&0777)
 }
 
-func unixModeToFileMode(m uint32) os.FileMode {
-	mode := os.FileMode(m & 0777)
+func unixModeToFileMode(m uint32) fs.FileMode {
+	mode := fs.FileMode(m & 0777)
 	switch m & s_IFMT {
 	case s_IFBLK:
-		mode |= os.ModeDevice
+		mode |= fs.ModeDevice
 	case s_IFCHR:
-		mode |= os.ModeDevice | os.ModeCharDevice
+		mode |= fs.ModeDevice | fs.ModeCharDevice
 	case s_IFDIR:
-		mode |= os.ModeDir
+		mode |= fs.ModeDir
 	case s_IFIFO:
-		mode |= os.ModeNamedPipe
+		mode |= fs.ModeNamedPipe
 	case s_IFLNK:
-		mode |= os.ModeSymlink
+		mode |= fs.ModeSymlink
 	case s_IFREG:
 		// nothing to do
 	case s_IFSOCK:
-		mode |= os.ModeSocket
+		mode |= fs.ModeSocket
 	}
 	if m&s_ISGID != 0 {
-		mode |= os.ModeSetgid
+		mode |= fs.ModeSetgid
 	}
 	if m&s_ISUID != 0 {
-		mode |= os.ModeSetuid
+		mode |= fs.ModeSetuid
 	}
 	if m&s_ISVTX != 0 {
-		mode |= os.ModeSticky
+		mode |= fs.ModeSticky
 	}
 	return mode
 }
diff --git a/src/archive/zip/writer_test.go b/src/archive/zip/writer_test.go
index 1fedfd8..282f9ec 100644
--- a/src/archive/zip/writer_test.go
+++ b/src/archive/zip/writer_test.go
@@ -9,9 +9,9 @@
 	"encoding/binary"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"math/rand"
-	"os"
 	"strings"
 	"testing"
 	"time"
@@ -23,7 +23,7 @@
 	Name   string
 	Data   []byte
 	Method uint16
-	Mode   os.FileMode
+	Mode   fs.FileMode
 }
 
 var writeTests = []WriteTest{
@@ -43,19 +43,19 @@
 		Name:   "setuid",
 		Data:   []byte("setuid file"),
 		Method: Deflate,
-		Mode:   0755 | os.ModeSetuid,
+		Mode:   0755 | fs.ModeSetuid,
 	},
 	{
 		Name:   "setgid",
 		Data:   []byte("setgid file"),
 		Method: Deflate,
-		Mode:   0755 | os.ModeSetgid,
+		Mode:   0755 | fs.ModeSetgid,
 	},
 	{
 		Name:   "symlink",
 		Data:   []byte("../link/target"),
 		Method: Deflate,
-		Mode:   0755 | os.ModeSymlink,
+		Mode:   0755 | fs.ModeSymlink,
 	},
 }
 
diff --git a/src/cmd/doc/pkg.go b/src/cmd/doc/pkg.go
index ffc302c..c2e06eb 100644
--- a/src/cmd/doc/pkg.go
+++ b/src/cmd/doc/pkg.go
@@ -16,8 +16,8 @@
 	"go/printer"
 	"go/token"
 	"io"
+	"io/fs"
 	"log"
-	"os"
 	"path/filepath"
 	"strings"
 	"unicode"
@@ -129,11 +129,10 @@
 // parsePackage turns the build package we found into a parsed package
 // we can then use to generate documentation.
 func parsePackage(writer io.Writer, pkg *build.Package, userPath string) *Package {
-	fs := token.NewFileSet()
 	// include tells parser.ParseDir which files to include.
 	// That means the file must be in the build package's GoFiles or CgoFiles
 	// list only (no tag-ignored files, tests, swig or other non-Go files).
-	include := func(info os.FileInfo) bool {
+	include := func(info fs.FileInfo) bool {
 		for _, name := range pkg.GoFiles {
 			if name == info.Name() {
 				return true
@@ -146,7 +145,8 @@
 		}
 		return false
 	}
-	pkgs, err := parser.ParseDir(fs, pkg.Dir, include, parser.ParseComments)
+	fset := token.NewFileSet()
+	pkgs, err := parser.ParseDir(fset, pkg.Dir, include, parser.ParseComments)
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -203,7 +203,7 @@
 		typedValue:  typedValue,
 		constructor: constructor,
 		build:       pkg,
-		fs:          fs,
+		fs:          fset,
 	}
 	p.buf.pkg = p
 	return p
diff --git a/src/cmd/fix/main.go b/src/cmd/fix/main.go
index d19dde6..dfba902 100644
--- a/src/cmd/fix/main.go
+++ b/src/cmd/fix/main.go
@@ -13,6 +13,7 @@
 	"go/parser"
 	"go/scanner"
 	"go/token"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -235,7 +236,7 @@
 	filepath.Walk(path, visitFile)
 }
 
-func visitFile(path string, f os.FileInfo, err error) error {
+func visitFile(path string, f fs.FileInfo, err error) error {
 	if err == nil && isGoFile(f) {
 		err = processFile(path, false)
 	}
@@ -245,7 +246,7 @@
 	return nil
 }
 
-func isGoFile(f os.FileInfo) bool {
+func isGoFile(f fs.FileInfo) bool {
 	// ignore non-Go files
 	name := f.Name()
 	return !f.IsDir() && !strings.HasPrefix(name, ".") && strings.HasSuffix(name, ".go")
diff --git a/src/cmd/go/go_test.go b/src/cmd/go/go_test.go
index 093ea2f..2c11d16 100644
--- a/src/cmd/go/go_test.go
+++ b/src/cmd/go/go_test.go
@@ -15,6 +15,7 @@
 	"internal/race"
 	"internal/testenv"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"log"
 	"os"
@@ -813,7 +814,7 @@
 func removeAll(dir string) error {
 	// module cache has 0444 directories;
 	// make them writable in order to remove content.
-	filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
+	filepath.Walk(dir, func(path string, info fs.FileInfo, err error) error {
 		// chmod not only directories, but also things that we couldn't even stat
 		// due to permission errors: they may also be unreadable directories.
 		if err != nil || info.IsDir() {
@@ -860,7 +861,7 @@
 		srcdir := filepath.Join(testGOROOT, copydir)
 		tg.tempDir(filepath.Join("goroot", copydir))
 		err := filepath.Walk(srcdir,
-			func(path string, info os.FileInfo, err error) error {
+			func(path string, info fs.FileInfo, err error) error {
 				if err != nil {
 					return err
 				}
@@ -2018,7 +2019,7 @@
 	tg.run("build", "-o", exe, "p")
 }
 
-func copyFile(src, dst string, perm os.FileMode) error {
+func copyFile(src, dst string, perm fs.FileMode) error {
 	sf, err := os.Open(src)
 	if err != nil {
 		return err
diff --git a/src/cmd/go/internal/cache/cache.go b/src/cmd/go/internal/cache/cache.go
index 15545ac..5464fe5 100644
--- a/src/cmd/go/internal/cache/cache.go
+++ b/src/cmd/go/internal/cache/cache.go
@@ -12,6 +12,7 @@
 	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -54,7 +55,7 @@
 		return nil, err
 	}
 	if !info.IsDir() {
-		return nil, &os.PathError{Op: "open", Path: dir, Err: fmt.Errorf("not a directory")}
+		return nil, &fs.PathError{Op: "open", Path: dir, Err: fmt.Errorf("not a directory")}
 	}
 	for i := 0; i < 256; i++ {
 		name := filepath.Join(dir, fmt.Sprintf("%02x", i))
diff --git a/src/cmd/go/internal/fsys/fsys.go b/src/cmd/go/internal/fsys/fsys.go
index 489af93..67359ff 100644
--- a/src/cmd/go/internal/fsys/fsys.go
+++ b/src/cmd/go/internal/fsys/fsys.go
@@ -6,6 +6,7 @@
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -240,7 +241,7 @@
 // readDir reads a dir on disk, returning an error that is errNotDir if the dir is not a directory.
 // Unfortunately, the error returned by ioutil.ReadDir if dir is not a directory
 // can vary depending on the OS (Linux, Mac, Windows return ENOTDIR; BSD returns EINVAL).
-func readDir(dir string) ([]os.FileInfo, error) {
+func readDir(dir string) ([]fs.FileInfo, error) {
 	fis, err := ioutil.ReadDir(dir)
 	if err == nil {
 		return fis, nil
@@ -249,25 +250,25 @@
 	if os.IsNotExist(err) {
 		return nil, err
 	} else if dirfi, staterr := os.Stat(dir); staterr == nil && !dirfi.IsDir() {
-		return nil, &os.PathError{Op: "ReadDir", Path: dir, Err: errNotDir}
+		return nil, &fs.PathError{Op: "ReadDir", Path: dir, Err: errNotDir}
 	} else {
 		return nil, err
 	}
 }
 
-// ReadDir provides a slice of os.FileInfo entries corresponding
+// ReadDir provides a slice of fs.FileInfo entries corresponding
 // to the overlaid files in the directory.
-func ReadDir(dir string) ([]os.FileInfo, error) {
+func ReadDir(dir string) ([]fs.FileInfo, error) {
 	dir = canonicalize(dir)
 	if _, ok := parentIsOverlayFile(dir); ok {
-		return nil, &os.PathError{Op: "ReadDir", Path: dir, Err: errNotDir}
+		return nil, &fs.PathError{Op: "ReadDir", Path: dir, Err: errNotDir}
 	}
 
 	dirNode := overlay[dir]
 	if dirNode == nil {
 		return readDir(dir)
 	} else if dirNode.isDeleted() {
-		return nil, &os.PathError{Op: "ReadDir", Path: dir, Err: os.ErrNotExist}
+		return nil, &fs.PathError{Op: "ReadDir", Path: dir, Err: fs.ErrNotExist}
 	}
 	diskfis, err := readDir(dir)
 	if err != nil && !os.IsNotExist(err) && !errors.Is(err, errNotDir) {
@@ -275,7 +276,7 @@
 	}
 
 	// Stat files in overlay to make composite list of fileinfos
-	files := make(map[string]os.FileInfo)
+	files := make(map[string]fs.FileInfo)
 	for _, f := range diskfis {
 		files[f.Name()] = f
 	}
@@ -327,14 +328,14 @@
 	cpath := canonicalize(path)
 	if node, ok := overlay[cpath]; ok {
 		if node.isDir() {
-			return nil, &os.PathError{Op: "Open", Path: path, Err: errors.New("fsys.Open doesn't support opening directories yet")}
+			return nil, &fs.PathError{Op: "Open", Path: path, Err: errors.New("fsys.Open doesn't support opening directories yet")}
 		}
 		return os.Open(node.actualFilePath)
 	} else if parent, ok := parentIsOverlayFile(filepath.Dir(cpath)); ok {
 		// The file is deleted explicitly in the Replace map,
 		// or implicitly because one of its parent directories was
 		// replaced by a file.
-		return nil, &os.PathError{
+		return nil, &fs.PathError{
 			Op:   "Open",
 			Path: path,
 			Err:  fmt.Errorf("file %s does not exist: parent directory %s is replaced by a file in overlay", path, parent)}
@@ -387,7 +388,7 @@
 
 // walk recursively descends path, calling walkFn. Copied, with some
 // modifications from path/filepath.walk.
-func walk(path string, info os.FileInfo, walkFn filepath.WalkFunc) error {
+func walk(path string, info fs.FileInfo, walkFn filepath.WalkFunc) error {
 	if !info.IsDir() {
 		return walkFn(path, info, nil)
 	}
@@ -432,11 +433,11 @@
 }
 
 // lstat implements a version of os.Lstat that operates on the overlay filesystem.
-func lstat(path string) (os.FileInfo, error) {
+func lstat(path string) (fs.FileInfo, error) {
 	cpath := canonicalize(path)
 
 	if _, ok := parentIsOverlayFile(filepath.Dir(cpath)); ok {
-		return nil, &os.PathError{Op: "lstat", Path: cpath, Err: os.ErrNotExist}
+		return nil, &fs.PathError{Op: "lstat", Path: cpath, Err: fs.ErrNotExist}
 	}
 
 	node, ok := overlay[cpath]
@@ -447,7 +448,7 @@
 
 	switch {
 	case node.isDeleted():
-		return nil, &os.PathError{Op: "lstat", Path: cpath, Err: os.ErrNotExist}
+		return nil, &fs.PathError{Op: "lstat", Path: cpath, Err: fs.ErrNotExist}
 	case node.isDir():
 		return fakeDir(filepath.Base(cpath)), nil
 	default:
@@ -459,22 +460,22 @@
 	}
 }
 
-// fakeFile provides an os.FileInfo implementation for an overlaid file,
+// fakeFile provides an fs.FileInfo implementation for an overlaid file,
 // so that the file has the name of the overlaid file, but takes all
 // other characteristics of the replacement file.
 type fakeFile struct {
 	name string
-	real os.FileInfo
+	real fs.FileInfo
 }
 
 func (f fakeFile) Name() string       { return f.name }
 func (f fakeFile) Size() int64        { return f.real.Size() }
-func (f fakeFile) Mode() os.FileMode  { return f.real.Mode() }
+func (f fakeFile) Mode() fs.FileMode  { return f.real.Mode() }
 func (f fakeFile) ModTime() time.Time { return f.real.ModTime() }
 func (f fakeFile) IsDir() bool        { return f.real.IsDir() }
 func (f fakeFile) Sys() interface{}   { return f.real.Sys() }
 
-// missingFile provides an os.FileInfo for an overlaid file where the
+// missingFile provides an fs.FileInfo for an overlaid file where the
 // destination file in the overlay doesn't exist. It returns zero values
 // for the fileInfo methods other than Name, set to the file's name, and Mode
 // set to ModeIrregular.
@@ -482,19 +483,19 @@
 
 func (f missingFile) Name() string       { return string(f) }
 func (f missingFile) Size() int64        { return 0 }
-func (f missingFile) Mode() os.FileMode  { return os.ModeIrregular }
+func (f missingFile) Mode() fs.FileMode  { return fs.ModeIrregular }
 func (f missingFile) ModTime() time.Time { return time.Unix(0, 0) }
 func (f missingFile) IsDir() bool        { return false }
 func (f missingFile) Sys() interface{}   { return nil }
 
-// fakeDir provides an os.FileInfo implementation for directories that are
+// fakeDir provides an fs.FileInfo implementation for directories that are
 // implicitly created by overlaid files. Each directory in the
 // path of an overlaid file is considered to exist in the overlay filesystem.
 type fakeDir string
 
 func (f fakeDir) Name() string       { return string(f) }
 func (f fakeDir) Size() int64        { return 0 }
-func (f fakeDir) Mode() os.FileMode  { return os.ModeDir | 0500 }
+func (f fakeDir) Mode() fs.FileMode  { return fs.ModeDir | 0500 }
 func (f fakeDir) ModTime() time.Time { return time.Unix(0, 0) }
 func (f fakeDir) IsDir() bool        { return true }
 func (f fakeDir) Sys() interface{}   { return nil }
diff --git a/src/cmd/go/internal/fsys/fsys_test.go b/src/cmd/go/internal/fsys/fsys_test.go
index 6cf59fb..ba9f05d 100644
--- a/src/cmd/go/internal/fsys/fsys_test.go
+++ b/src/cmd/go/internal/fsys/fsys_test.go
@@ -6,6 +6,7 @@
 	"errors"
 	"fmt"
 	"internal/testenv"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -291,8 +292,8 @@
 		_, gotErr := ReadDir(dir)
 		if gotErr == nil {
 			t.Errorf("ReadDir(%q): got no error, want error", dir)
-		} else if _, ok := gotErr.(*os.PathError); !ok {
-			t.Errorf("ReadDir(%q): got error with string %q and type %T, want os.PathError", dir, gotErr.Error(), gotErr)
+		} else if _, ok := gotErr.(*fs.PathError); !ok {
+			t.Errorf("ReadDir(%q): got error with string %q and type %T, want fs.PathError", dir, gotErr.Error(), gotErr)
 		}
 	}
 }
@@ -489,7 +490,7 @@
 		path  string
 		name  string
 		size  int64
-		mode  os.FileMode
+		mode  fs.FileMode
 		isDir bool
 	}
 	testCases := []struct {
@@ -504,7 +505,7 @@
 `,
 			".",
 			[]file{
-				{".", "root", 0, os.ModeDir | 0700, true},
+				{".", "root", 0, fs.ModeDir | 0700, true},
 				{"file.txt", "file.txt", 0, 0600, false},
 			},
 		},
@@ -520,7 +521,7 @@
 `,
 			".",
 			[]file{
-				{".", "root", 0, os.ModeDir | 0500, true},
+				{".", "root", 0, fs.ModeDir | 0500, true},
 				{"file.txt", "file.txt", 23, 0600, false},
 				{"other.txt", "other.txt", 23, 0600, false},
 			},
@@ -536,7 +537,7 @@
 `,
 			".",
 			[]file{
-				{".", "root", 0, os.ModeDir | 0500, true},
+				{".", "root", 0, fs.ModeDir | 0500, true},
 				{"file.txt", "file.txt", 23, 0600, false},
 				{"other.txt", "other.txt", 23, 0600, false},
 			},
@@ -552,8 +553,8 @@
 `,
 			".",
 			[]file{
-				{".", "root", 0, os.ModeDir | 0500, true},
-				{"dir", "dir", 0, os.ModeDir | 0500, true},
+				{".", "root", 0, fs.ModeDir | 0500, true},
+				{"dir", "dir", 0, fs.ModeDir | 0500, true},
 				{"dir" + string(filepath.Separator) + "file.txt", "file.txt", 23, 0600, false},
 				{"other.txt", "other.txt", 23, 0600, false},
 			},
@@ -565,7 +566,7 @@
 			initOverlay(t, tc.overlay)
 
 			var got []file
-			Walk(tc.root, func(path string, info os.FileInfo, err error) error {
+			Walk(tc.root, func(path string, info fs.FileInfo, err error) error {
 				got = append(got, file{path, info.Name(), info.Size(), info.Mode(), info.IsDir()})
 				return nil
 			})
@@ -580,8 +581,8 @@
 				if got[i].name != tc.wantFiles[i].name {
 					t.Errorf("name of file #%v in walk, got %q, want %q", i, got[i].name, tc.wantFiles[i].name)
 				}
-				if got[i].mode&(os.ModeDir|0700) != tc.wantFiles[i].mode {
-					t.Errorf("mode&(os.ModeDir|0700) for mode of file #%v in walk, got %v, want %v", i, got[i].mode&(os.ModeDir|0700), tc.wantFiles[i].mode)
+				if got[i].mode&(fs.ModeDir|0700) != tc.wantFiles[i].mode {
+					t.Errorf("mode&(fs.ModeDir|0700) for mode of file #%v in walk, got %v, want %v", i, got[i].mode&(fs.ModeDir|0700), tc.wantFiles[i].mode)
 				}
 				if got[i].isDir != tc.wantFiles[i].isDir {
 					t.Errorf("isDir for file #%v in walk, got %v, want %v", i, got[i].isDir, tc.wantFiles[i].isDir)
@@ -610,7 +611,7 @@
 `)
 
 	var seen []string
-	Walk(".", func(path string, info os.FileInfo, err error) error {
+	Walk(".", func(path string, info fs.FileInfo, err error) error {
 		seen = append(seen, path)
 		if path == "skipthisdir" || path == filepath.Join("dontskip", "skip") {
 			return filepath.SkipDir
@@ -635,7 +636,7 @@
 	initOverlay(t, "{}")
 
 	alreadyCalled := false
-	err := Walk("foo", func(path string, info os.FileInfo, err error) error {
+	err := Walk("foo", func(path string, info fs.FileInfo, err error) error {
 		if alreadyCalled {
 			t.Fatal("expected walk function to be called exactly once, but it was called more than once")
 		}
@@ -683,7 +684,7 @@
 		t.Run(tc.name, func(t *testing.T) {
 			var got []string
 
-			err := Walk(tc.dir, func(path string, info os.FileInfo, err error) error {
+			err := Walk(tc.dir, func(path string, info fs.FileInfo, err error) error {
 				got = append(got, path)
 				if err != nil {
 					t.Errorf("walkfn: got non nil err argument: %v, want nil err argument", err)
@@ -706,7 +707,7 @@
 	type file struct {
 		name  string
 		size  int64
-		mode  os.FileMode // mode & (os.ModeDir|0x700): only check 'user' permissions
+		mode  fs.FileMode // mode & (fs.ModeDir|0x700): only check 'user' permissions
 		isDir bool
 	}
 
@@ -771,7 +772,7 @@
 -- dir/foo.txt --
 `,
 			"dir",
-			file{"dir", 0, 0700 | os.ModeDir, true},
+			file{"dir", 0, 0700 | fs.ModeDir, true},
 			false,
 		},
 		{
@@ -780,7 +781,7 @@
 -- dummy.txt --
 `,
 			"dir",
-			file{"dir", 0, 0500 | os.ModeDir, true},
+			file{"dir", 0, 0500 | fs.ModeDir, true},
 			false,
 		},
 	}
@@ -801,8 +802,8 @@
 			if got.Name() != tc.want.name {
 				t.Errorf("lstat(%q).Name(): got %q, want %q", tc.path, got.Name(), tc.want.name)
 			}
-			if got.Mode()&(os.ModeDir|0700) != tc.want.mode {
-				t.Errorf("lstat(%q).Mode()&(os.ModeDir|0700): got %v, want %v", tc.path, got.Mode()&(os.ModeDir|0700), tc.want.mode)
+			if got.Mode()&(fs.ModeDir|0700) != tc.want.mode {
+				t.Errorf("lstat(%q).Mode()&(fs.ModeDir|0700): got %v, want %v", tc.path, got.Mode()&(fs.ModeDir|0700), tc.want.mode)
 			}
 			if got.IsDir() != tc.want.isDir {
 				t.Errorf("lstat(%q).IsDir(): got %v, want %v", tc.path, got.IsDir(), tc.want.isDir)
diff --git a/src/cmd/go/internal/imports/scan.go b/src/cmd/go/internal/imports/scan.go
index 42ee49a..d45393f 100644
--- a/src/cmd/go/internal/imports/scan.go
+++ b/src/cmd/go/internal/imports/scan.go
@@ -6,6 +6,7 @@
 
 import (
 	"fmt"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"sort"
@@ -26,7 +27,7 @@
 
 		// If the directory entry is a symlink, stat it to obtain the info for the
 		// link target instead of the link itself.
-		if info.Mode()&os.ModeSymlink != 0 {
+		if info.Mode()&fs.ModeSymlink != 0 {
 			info, err = os.Stat(filepath.Join(dir, name))
 			if err != nil {
 				continue // Ignore broken symlinks.
diff --git a/src/cmd/go/internal/load/pkg.go b/src/cmd/go/internal/load/pkg.go
index f73b79d..066ff6c 100644
--- a/src/cmd/go/internal/load/pkg.go
+++ b/src/cmd/go/internal/load/pkg.go
@@ -14,6 +14,7 @@
 	"go/build"
 	"go/scanner"
 	"go/token"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	pathpkg "path"
@@ -2300,7 +2301,7 @@
 	// to make it look like this is a standard package or
 	// command directory. So that local imports resolve
 	// consistently, the files must all be in the same directory.
-	var dirent []os.FileInfo
+	var dirent []fs.FileInfo
 	var dir string
 	for _, file := range gofiles {
 		fi, err := os.Stat(file)
@@ -2321,7 +2322,7 @@
 		}
 		dirent = append(dirent, fi)
 	}
-	ctxt.ReadDir = func(string) ([]os.FileInfo, error) { return dirent, nil }
+	ctxt.ReadDir = func(string) ([]fs.FileInfo, error) { return dirent, nil }
 
 	if cfg.ModulesEnabled {
 		modload.ImportFromFiles(ctx, gofiles)
diff --git a/src/cmd/go/internal/lockedfile/internal/filelock/filelock.go b/src/cmd/go/internal/lockedfile/internal/filelock/filelock.go
index aba3eed..05f27c3 100644
--- a/src/cmd/go/internal/lockedfile/internal/filelock/filelock.go
+++ b/src/cmd/go/internal/lockedfile/internal/filelock/filelock.go
@@ -9,6 +9,7 @@
 
 import (
 	"errors"
+	"io/fs"
 	"os"
 )
 
@@ -24,7 +25,7 @@
 	Fd() uintptr
 
 	// Stat returns the FileInfo structure describing file.
-	Stat() (os.FileInfo, error)
+	Stat() (fs.FileInfo, error)
 }
 
 // Lock places an advisory write lock on the file, blocking until it can be
@@ -87,7 +88,7 @@
 // underlyingError returns the underlying error for known os error types.
 func underlyingError(err error) error {
 	switch err := err.(type) {
-	case *os.PathError:
+	case *fs.PathError:
 		return err.Err
 	case *os.LinkError:
 		return err.Err
diff --git a/src/cmd/go/internal/lockedfile/internal/filelock/filelock_fcntl.go b/src/cmd/go/internal/lockedfile/internal/filelock/filelock_fcntl.go
index 8776c57..1fa4327 100644
--- a/src/cmd/go/internal/lockedfile/internal/filelock/filelock_fcntl.go
+++ b/src/cmd/go/internal/lockedfile/internal/filelock/filelock_fcntl.go
@@ -18,8 +18,8 @@
 import (
 	"errors"
 	"io"
+	"io/fs"
 	"math/rand"
-	"os"
 	"sync"
 	"syscall"
 	"time"
@@ -61,7 +61,7 @@
 	mu.Lock()
 	if i, dup := inodes[f]; dup && i != ino {
 		mu.Unlock()
-		return &os.PathError{
+		return &fs.PathError{
 			Op:   lt.String(),
 			Path: f.Name(),
 			Err:  errors.New("inode for file changed since last Lock or RLock"),
@@ -152,7 +152,7 @@
 
 	if err != nil {
 		unlock(f)
-		return &os.PathError{
+		return &fs.PathError{
 			Op:   lt.String(),
 			Path: f.Name(),
 			Err:  err,
diff --git a/src/cmd/go/internal/lockedfile/internal/filelock/filelock_other.go b/src/cmd/go/internal/lockedfile/internal/filelock/filelock_other.go
index 107611e..bc48034 100644
--- a/src/cmd/go/internal/lockedfile/internal/filelock/filelock_other.go
+++ b/src/cmd/go/internal/lockedfile/internal/filelock/filelock_other.go
@@ -6,7 +6,7 @@
 
 package filelock
 
-import "os"
+import "io/fs"
 
 type lockType int8
 
@@ -16,7 +16,7 @@
 )
 
 func lock(f File, lt lockType) error {
-	return &os.PathError{
+	return &fs.PathError{
 		Op:   lt.String(),
 		Path: f.Name(),
 		Err:  ErrNotSupported,
@@ -24,7 +24,7 @@
 }
 
 func unlock(f File) error {
-	return &os.PathError{
+	return &fs.PathError{
 		Op:   "Unlock",
 		Path: f.Name(),
 		Err:  ErrNotSupported,
diff --git a/src/cmd/go/internal/lockedfile/internal/filelock/filelock_plan9.go b/src/cmd/go/internal/lockedfile/internal/filelock/filelock_plan9.go
index afdffe3..0798ee4 100644
--- a/src/cmd/go/internal/lockedfile/internal/filelock/filelock_plan9.go
+++ b/src/cmd/go/internal/lockedfile/internal/filelock/filelock_plan9.go
@@ -6,9 +6,7 @@
 
 package filelock
 
-import (
-	"os"
-)
+import "io/fs"
 
 type lockType int8
 
@@ -18,7 +16,7 @@
 )
 
 func lock(f File, lt lockType) error {
-	return &os.PathError{
+	return &fs.PathError{
 		Op:   lt.String(),
 		Path: f.Name(),
 		Err:  ErrNotSupported,
@@ -26,7 +24,7 @@
 }
 
 func unlock(f File) error {
-	return &os.PathError{
+	return &fs.PathError{
 		Op:   "Unlock",
 		Path: f.Name(),
 		Err:  ErrNotSupported,
diff --git a/src/cmd/go/internal/lockedfile/internal/filelock/filelock_unix.go b/src/cmd/go/internal/lockedfile/internal/filelock/filelock_unix.go
index 78f2c51..ed07bac 100644
--- a/src/cmd/go/internal/lockedfile/internal/filelock/filelock_unix.go
+++ b/src/cmd/go/internal/lockedfile/internal/filelock/filelock_unix.go
@@ -7,7 +7,7 @@
 package filelock
 
 import (
-	"os"
+	"io/fs"
 	"syscall"
 )
 
@@ -26,7 +26,7 @@
 		}
 	}
 	if err != nil {
-		return &os.PathError{
+		return &fs.PathError{
 			Op:   lt.String(),
 			Path: f.Name(),
 			Err:  err,
diff --git a/src/cmd/go/internal/lockedfile/internal/filelock/filelock_windows.go b/src/cmd/go/internal/lockedfile/internal/filelock/filelock_windows.go
index 43e85e4..19de27e 100644
--- a/src/cmd/go/internal/lockedfile/internal/filelock/filelock_windows.go
+++ b/src/cmd/go/internal/lockedfile/internal/filelock/filelock_windows.go
@@ -8,7 +8,7 @@
 
 import (
 	"internal/syscall/windows"
-	"os"
+	"io/fs"
 	"syscall"
 )
 
@@ -34,7 +34,7 @@
 
 	err := windows.LockFileEx(syscall.Handle(f.Fd()), uint32(lt), reserved, allBytes, allBytes, ol)
 	if err != nil {
-		return &os.PathError{
+		return &fs.PathError{
 			Op:   lt.String(),
 			Path: f.Name(),
 			Err:  err,
@@ -47,7 +47,7 @@
 	ol := new(syscall.Overlapped)
 	err := windows.UnlockFileEx(syscall.Handle(f.Fd()), reserved, allBytes, allBytes, ol)
 	if err != nil {
-		return &os.PathError{
+		return &fs.PathError{
 			Op:   "Unlock",
 			Path: f.Name(),
 			Err:  err,
diff --git a/src/cmd/go/internal/lockedfile/lockedfile.go b/src/cmd/go/internal/lockedfile/lockedfile.go
index 59b2dba..503024d 100644
--- a/src/cmd/go/internal/lockedfile/lockedfile.go
+++ b/src/cmd/go/internal/lockedfile/lockedfile.go
@@ -9,6 +9,7 @@
 import (
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"runtime"
@@ -35,7 +36,7 @@
 // OpenFile is like os.OpenFile, but returns a locked file.
 // If flag includes os.O_WRONLY or os.O_RDWR, the file is write-locked;
 // otherwise, it is read-locked.
-func OpenFile(name string, flag int, perm os.FileMode) (*File, error) {
+func OpenFile(name string, flag int, perm fs.FileMode) (*File, error) {
 	var (
 		f   = new(File)
 		err error
@@ -82,10 +83,10 @@
 // non-nil error.
 func (f *File) Close() error {
 	if f.closed {
-		return &os.PathError{
+		return &fs.PathError{
 			Op:   "close",
 			Path: f.Name(),
-			Err:  os.ErrClosed,
+			Err:  fs.ErrClosed,
 		}
 	}
 	f.closed = true
@@ -108,7 +109,7 @@
 
 // Write opens the named file (creating it with the given permissions if needed),
 // then write-locks it and overwrites it with the given content.
-func Write(name string, content io.Reader, perm os.FileMode) (err error) {
+func Write(name string, content io.Reader, perm fs.FileMode) (err error) {
 	f, err := OpenFile(name, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, perm)
 	if err != nil {
 		return err
diff --git a/src/cmd/go/internal/lockedfile/lockedfile_filelock.go b/src/cmd/go/internal/lockedfile/lockedfile_filelock.go
index f63dd86..10e1240 100644
--- a/src/cmd/go/internal/lockedfile/lockedfile_filelock.go
+++ b/src/cmd/go/internal/lockedfile/lockedfile_filelock.go
@@ -7,12 +7,13 @@
 package lockedfile
 
 import (
+	"io/fs"
 	"os"
 
 	"cmd/go/internal/lockedfile/internal/filelock"
 )
 
-func openFile(name string, flag int, perm os.FileMode) (*os.File, error) {
+func openFile(name string, flag int, perm fs.FileMode) (*os.File, error) {
 	// On BSD systems, we could add the O_SHLOCK or O_EXLOCK flag to the OpenFile
 	// call instead of locking separately, but we have to support separate locking
 	// calls for Linux and Windows anyway, so it's simpler to use that approach
diff --git a/src/cmd/go/internal/lockedfile/lockedfile_plan9.go b/src/cmd/go/internal/lockedfile/lockedfile_plan9.go
index 4a52c94..5168138 100644
--- a/src/cmd/go/internal/lockedfile/lockedfile_plan9.go
+++ b/src/cmd/go/internal/lockedfile/lockedfile_plan9.go
@@ -7,6 +7,7 @@
 package lockedfile
 
 import (
+	"io/fs"
 	"math/rand"
 	"os"
 	"strings"
@@ -41,7 +42,7 @@
 	return false
 }
 
-func openFile(name string, flag int, perm os.FileMode) (*os.File, error) {
+func openFile(name string, flag int, perm fs.FileMode) (*os.File, error) {
 	// Plan 9 uses a mode bit instead of explicit lock/unlock syscalls.
 	//
 	// Per http://man.cat-v.org/plan_9/5/stat: “Exclusive use files may be open
@@ -56,8 +57,8 @@
 	// have the ModeExclusive bit set. Set it before we call OpenFile, so that we
 	// can be confident that a successful OpenFile implies exclusive use.
 	if fi, err := os.Stat(name); err == nil {
-		if fi.Mode()&os.ModeExclusive == 0 {
-			if err := os.Chmod(name, fi.Mode()|os.ModeExclusive); err != nil {
+		if fi.Mode()&fs.ModeExclusive == 0 {
+			if err := os.Chmod(name, fi.Mode()|fs.ModeExclusive); err != nil {
 				return nil, err
 			}
 		}
@@ -68,7 +69,7 @@
 	nextSleep := 1 * time.Millisecond
 	const maxSleep = 500 * time.Millisecond
 	for {
-		f, err := os.OpenFile(name, flag, perm|os.ModeExclusive)
+		f, err := os.OpenFile(name, flag, perm|fs.ModeExclusive)
 		if err == nil {
 			return f, nil
 		}
diff --git a/src/cmd/go/internal/modcmd/vendor.go b/src/cmd/go/internal/modcmd/vendor.go
index 1bc4ab3..1b9ce60 100644
--- a/src/cmd/go/internal/modcmd/vendor.go
+++ b/src/cmd/go/internal/modcmd/vendor.go
@@ -9,6 +9,7 @@
 	"context"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -232,7 +233,7 @@
 }
 
 // matchMetadata reports whether info is a metadata file.
-func matchMetadata(dir string, info os.FileInfo) bool {
+func matchMetadata(dir string, info fs.FileInfo) bool {
 	name := info.Name()
 	for _, p := range metaPrefixes {
 		if strings.HasPrefix(name, p) {
@@ -243,7 +244,7 @@
 }
 
 // matchPotentialSourceFile reports whether info may be relevant to a build operation.
-func matchPotentialSourceFile(dir string, info os.FileInfo) bool {
+func matchPotentialSourceFile(dir string, info fs.FileInfo) bool {
 	if strings.HasSuffix(info.Name(), "_test.go") {
 		return false
 	}
@@ -269,7 +270,7 @@
 }
 
 // copyDir copies all regular files satisfying match(info) from src to dst.
-func copyDir(dst, src string, match func(dir string, info os.FileInfo) bool) {
+func copyDir(dst, src string, match func(dir string, info fs.FileInfo) bool) {
 	files, err := ioutil.ReadDir(src)
 	if err != nil {
 		base.Fatalf("go mod vendor: %v", err)
diff --git a/src/cmd/go/internal/modcmd/verify.go b/src/cmd/go/internal/modcmd/verify.go
index bd591d3..ce24793 100644
--- a/src/cmd/go/internal/modcmd/verify.go
+++ b/src/cmd/go/internal/modcmd/verify.go
@@ -9,6 +9,7 @@
 	"context"
 	"errors"
 	"fmt"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"runtime"
@@ -88,8 +89,8 @@
 	dir, dirErr := modfetch.DownloadDir(mod)
 	data, err := ioutil.ReadFile(zip + "hash")
 	if err != nil {
-		if zipErr != nil && errors.Is(zipErr, os.ErrNotExist) &&
-			dirErr != nil && errors.Is(dirErr, os.ErrNotExist) {
+		if zipErr != nil && errors.Is(zipErr, fs.ErrNotExist) &&
+			dirErr != nil && errors.Is(dirErr, fs.ErrNotExist) {
 			// Nothing downloaded yet. Nothing to verify.
 			return nil
 		}
@@ -98,7 +99,7 @@
 	}
 	h := string(bytes.TrimSpace(data))
 
-	if zipErr != nil && errors.Is(zipErr, os.ErrNotExist) {
+	if zipErr != nil && errors.Is(zipErr, fs.ErrNotExist) {
 		// ok
 	} else {
 		hZ, err := dirhash.HashZip(zip, dirhash.DefaultHash)
@@ -109,7 +110,7 @@
 			errs = append(errs, fmt.Errorf("%s %s: zip has been modified (%v)", mod.Path, mod.Version, zip))
 		}
 	}
-	if dirErr != nil && errors.Is(dirErr, os.ErrNotExist) {
+	if dirErr != nil && errors.Is(dirErr, fs.ErrNotExist) {
 		// ok
 	} else {
 		hD, err := dirhash.HashDir(dir, mod.Path+"@"+mod.Version, dirhash.DefaultHash)
diff --git a/src/cmd/go/internal/modfetch/cache.go b/src/cmd/go/internal/modfetch/cache.go
index 6eadb02..b7aa670 100644
--- a/src/cmd/go/internal/modfetch/cache.go
+++ b/src/cmd/go/internal/modfetch/cache.go
@@ -10,6 +10,7 @@
 	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -60,7 +61,7 @@
 
 // DownloadDir returns the directory to which m should have been downloaded.
 // An error will be returned if the module path or version cannot be escaped.
-// An error satisfying errors.Is(err, os.ErrNotExist) will be returned
+// An error satisfying errors.Is(err, fs.ErrNotExist) will be returned
 // along with the directory if the directory does not exist or if the directory
 // is not completely populated.
 func DownloadDir(m module.Version) (string, error) {
@@ -107,14 +108,14 @@
 // DownloadDirPartialError is returned by DownloadDir if a module directory
 // exists but was not completely populated.
 //
-// DownloadDirPartialError is equivalent to os.ErrNotExist.
+// DownloadDirPartialError is equivalent to fs.ErrNotExist.
 type DownloadDirPartialError struct {
 	Dir string
 	Err error
 }
 
 func (e *DownloadDirPartialError) Error() string     { return fmt.Sprintf("%s: %v", e.Dir, e.Err) }
-func (e *DownloadDirPartialError) Is(err error) bool { return err == os.ErrNotExist }
+func (e *DownloadDirPartialError) Is(err error) bool { return err == fs.ErrNotExist }
 
 // lockVersion locks a file within the module cache that guards the downloading
 // and extraction of the zipfile for the given module version.
diff --git a/src/cmd/go/internal/modfetch/codehost/codehost.go b/src/cmd/go/internal/modfetch/codehost/codehost.go
index df4cfdab..c5fbb31 100644
--- a/src/cmd/go/internal/modfetch/codehost/codehost.go
+++ b/src/cmd/go/internal/modfetch/codehost/codehost.go
@@ -11,6 +11,7 @@
 	"crypto/sha256"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -105,7 +106,7 @@
 	Err  error  // error if any; os.IsNotExist(Err)==true if rev exists but file does not exist in that rev
 }
 
-// UnknownRevisionError is an error equivalent to os.ErrNotExist, but for a
+// UnknownRevisionError is an error equivalent to fs.ErrNotExist, but for a
 // revision rather than a file.
 type UnknownRevisionError struct {
 	Rev string
@@ -115,10 +116,10 @@
 	return "unknown revision " + e.Rev
 }
 func (UnknownRevisionError) Is(err error) bool {
-	return err == os.ErrNotExist
+	return err == fs.ErrNotExist
 }
 
-// ErrNoCommits is an error equivalent to os.ErrNotExist indicating that a given
+// ErrNoCommits is an error equivalent to fs.ErrNotExist indicating that a given
 // repository or module contains no commits.
 var ErrNoCommits error = noCommitsError{}
 
@@ -128,7 +129,7 @@
 	return "no commits"
 }
 func (noCommitsError) Is(err error) bool {
-	return err == os.ErrNotExist
+	return err == fs.ErrNotExist
 }
 
 // AllHex reports whether the revision rev is entirely lower-case hexadecimal digits.
diff --git a/src/cmd/go/internal/modfetch/codehost/git.go b/src/cmd/go/internal/modfetch/codehost/git.go
index 5a35829..58b4b2f 100644
--- a/src/cmd/go/internal/modfetch/codehost/git.go
+++ b/src/cmd/go/internal/modfetch/codehost/git.go
@@ -9,6 +9,7 @@
 	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"net/url"
 	"os"
@@ -34,13 +35,13 @@
 }
 
 // A notExistError wraps another error to retain its original text
-// but makes it opaquely equivalent to os.ErrNotExist.
+// but makes it opaquely equivalent to fs.ErrNotExist.
 type notExistError struct {
 	err error
 }
 
 func (e notExistError) Error() string   { return e.err.Error() }
-func (notExistError) Is(err error) bool { return err == os.ErrNotExist }
+func (notExistError) Is(err error) bool { return err == fs.ErrNotExist }
 
 const gitWorkDirType = "git3"
 
@@ -188,7 +189,7 @@
 		// For HTTP and HTTPS, that's easy to detect: we'll try to fetch the URL
 		// ourselves and see what code it serves.
 		if u, err := url.Parse(r.remoteURL); err == nil && (u.Scheme == "http" || u.Scheme == "https") {
-			if _, err := web.GetBytes(u); errors.Is(err, os.ErrNotExist) {
+			if _, err := web.GetBytes(u); errors.Is(err, fs.ErrNotExist) {
 				gitErr = notExistError{gitErr}
 			}
 		}
@@ -505,7 +506,7 @@
 	}
 	out, err := Run(r.dir, "git", "cat-file", "blob", info.Name+":"+file)
 	if err != nil {
-		return nil, os.ErrNotExist
+		return nil, fs.ErrNotExist
 	}
 	return out, nil
 }
@@ -629,9 +630,9 @@
 		case "tag", "commit":
 			switch fileType {
 			default:
-				f.Err = &os.PathError{Path: tag + ":" + file, Op: "read", Err: fmt.Errorf("unexpected non-blob type %q", fileType)}
+				f.Err = &fs.PathError{Path: tag + ":" + file, Op: "read", Err: fmt.Errorf("unexpected non-blob type %q", fileType)}
 			case "missing":
-				f.Err = &os.PathError{Path: tag + ":" + file, Op: "read", Err: os.ErrNotExist}
+				f.Err = &fs.PathError{Path: tag + ":" + file, Op: "read", Err: fs.ErrNotExist}
 			case "blob":
 				f.Data = fileData
 			}
@@ -826,7 +827,7 @@
 	archive, err := Run(r.dir, "git", "-c", "core.autocrlf=input", "-c", "core.eol=lf", "archive", "--format=zip", "--prefix=prefix/", info.Name, args)
 	if err != nil {
 		if bytes.Contains(err.(*RunError).Stderr, []byte("did not match any files")) {
-			return nil, os.ErrNotExist
+			return nil, fs.ErrNotExist
 		}
 		return nil, err
 	}
diff --git a/src/cmd/go/internal/modfetch/codehost/git_test.go b/src/cmd/go/internal/modfetch/codehost/git_test.go
index ba27c70..16908b3 100644
--- a/src/cmd/go/internal/modfetch/codehost/git_test.go
+++ b/src/cmd/go/internal/modfetch/codehost/git_test.go
@@ -10,6 +10,7 @@
 	"flag"
 	"fmt"
 	"internal/testenv"
+	"io/fs"
 	"io/ioutil"
 	"log"
 	"os"
@@ -210,7 +211,7 @@
 		repo: gitrepo1,
 		rev:  "v2.3.4",
 		file: "another.txt",
-		err:  os.ErrNotExist.Error(),
+		err:  fs.ErrNotExist.Error(),
 	},
 }
 
diff --git a/src/cmd/go/internal/modfetch/codehost/vcs.go b/src/cmd/go/internal/modfetch/codehost/vcs.go
index 6278cb2..ec97fc7 100644
--- a/src/cmd/go/internal/modfetch/codehost/vcs.go
+++ b/src/cmd/go/internal/modfetch/codehost/vcs.go
@@ -9,6 +9,7 @@
 	"fmt"
 	"internal/lazyregexp"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -377,7 +378,7 @@
 
 	out, err := Run(r.dir, r.cmd.readFile(rev, file, r.remote))
 	if err != nil {
-		return nil, os.ErrNotExist
+		return nil, fs.ErrNotExist
 	}
 	return out, nil
 }
diff --git a/src/cmd/go/internal/modfetch/coderepo.go b/src/cmd/go/internal/modfetch/coderepo.go
index d99a31d..7f44e18 100644
--- a/src/cmd/go/internal/modfetch/coderepo.go
+++ b/src/cmd/go/internal/modfetch/coderepo.go
@@ -10,6 +10,7 @@
 	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path"
@@ -1040,7 +1041,7 @@
 }
 
 func (f zipFile) Path() string                 { return f.name }
-func (f zipFile) Lstat() (os.FileInfo, error)  { return f.f.FileInfo(), nil }
+func (f zipFile) Lstat() (fs.FileInfo, error)  { return f.f.FileInfo(), nil }
 func (f zipFile) Open() (io.ReadCloser, error) { return f.f.Open() }
 
 type dataFile struct {
@@ -1049,7 +1050,7 @@
 }
 
 func (f dataFile) Path() string                { return f.name }
-func (f dataFile) Lstat() (os.FileInfo, error) { return dataFileInfo{f}, nil }
+func (f dataFile) Lstat() (fs.FileInfo, error) { return dataFileInfo{f}, nil }
 func (f dataFile) Open() (io.ReadCloser, error) {
 	return ioutil.NopCloser(bytes.NewReader(f.data)), nil
 }
@@ -1060,7 +1061,7 @@
 
 func (fi dataFileInfo) Name() string       { return path.Base(fi.f.name) }
 func (fi dataFileInfo) Size() int64        { return int64(len(fi.f.data)) }
-func (fi dataFileInfo) Mode() os.FileMode  { return 0644 }
+func (fi dataFileInfo) Mode() fs.FileMode  { return 0644 }
 func (fi dataFileInfo) ModTime() time.Time { return time.Time{} }
 func (fi dataFileInfo) IsDir() bool        { return false }
 func (fi dataFileInfo) Sys() interface{}   { return nil }
diff --git a/src/cmd/go/internal/modfetch/fetch.go b/src/cmd/go/internal/modfetch/fetch.go
index 5994199..6ff455e 100644
--- a/src/cmd/go/internal/modfetch/fetch.go
+++ b/src/cmd/go/internal/modfetch/fetch.go
@@ -11,6 +11,7 @@
 	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -67,7 +68,7 @@
 	if err == nil {
 		// The directory has already been completely extracted (no .partial file exists).
 		return dir, nil
-	} else if dir == "" || !errors.Is(err, os.ErrNotExist) {
+	} else if dir == "" || !errors.Is(err, fs.ErrNotExist) {
 		return "", err
 	}
 
@@ -314,10 +315,10 @@
 func makeDirsReadOnly(dir string) {
 	type pathMode struct {
 		path string
-		mode os.FileMode
+		mode fs.FileMode
 	}
 	var dirs []pathMode // in lexical order
-	filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
+	filepath.Walk(dir, func(path string, info fs.FileInfo, err error) error {
 		if err == nil && info.Mode()&0222 != 0 {
 			if info.IsDir() {
 				dirs = append(dirs, pathMode{path, info.Mode()})
@@ -336,7 +337,7 @@
 // any permission changes needed to do so.
 func RemoveAll(dir string) error {
 	// Module cache has 0555 directories; make them writable in order to remove content.
-	filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
+	filepath.Walk(dir, func(path string, info fs.FileInfo, err error) error {
 		if err != nil {
 			return nil // ignore errors walking in file system
 		}
@@ -441,7 +442,7 @@
 	}
 	data, err := renameio.ReadFile(ziphash)
 	if err != nil {
-		if errors.Is(err, os.ErrNotExist) {
+		if errors.Is(err, fs.ErrNotExist) {
 			// This can happen if someone does rm -rf GOPATH/src/cache/download. So it goes.
 			return
 		}
diff --git a/src/cmd/go/internal/modfetch/proxy.go b/src/cmd/go/internal/modfetch/proxy.go
index 4ac2665..819990b 100644
--- a/src/cmd/go/internal/modfetch/proxy.go
+++ b/src/cmd/go/internal/modfetch/proxy.go
@@ -9,9 +9,9 @@
 	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"net/url"
-	"os"
 	"path"
 	pathpkg "path"
 	"path/filepath"
@@ -186,7 +186,7 @@
 
 // TryProxies iterates f over each configured proxy (including "noproxy" and
 // "direct" if applicable) until f returns no error or until f returns an
-// error that is not equivalent to os.ErrNotExist on a proxy configured
+// error that is not equivalent to fs.ErrNotExist on a proxy configured
 // not to fall back on errors.
 //
 // TryProxies then returns that final error.
@@ -222,7 +222,7 @@
 		if err == nil {
 			return nil
 		}
-		isNotExistErr := errors.Is(err, os.ErrNotExist)
+		isNotExistErr := errors.Is(err, fs.ErrNotExist)
 
 		if proxy.url == "direct" || (proxy.url == "noproxy" && err != errUseProxy) {
 			bestErr = err
@@ -428,7 +428,7 @@
 func (p *proxyRepo) Latest() (*RevInfo, error) {
 	data, err := p.getBytes("@latest")
 	if err != nil {
-		if !errors.Is(err, os.ErrNotExist) {
+		if !errors.Is(err, fs.ErrNotExist) {
 			return nil, p.versionError("", err)
 		}
 		return p.latest()
diff --git a/src/cmd/go/internal/modfetch/repo.go b/src/cmd/go/internal/modfetch/repo.go
index c7cf559..af9e24c 100644
--- a/src/cmd/go/internal/modfetch/repo.go
+++ b/src/cmd/go/internal/modfetch/repo.go
@@ -7,6 +7,7 @@
 import (
 	"fmt"
 	"io"
+	"io/fs"
 	"os"
 	"sort"
 	"strconv"
@@ -432,7 +433,7 @@
 func (r errRepo) GoMod(version string) ([]byte, error)              { return nil, r.err }
 func (r errRepo) Zip(dst io.Writer, version string) error           { return r.err }
 
-// A notExistError is like os.ErrNotExist, but with a custom message
+// A notExistError is like fs.ErrNotExist, but with a custom message
 type notExistError struct {
 	err error
 }
@@ -446,7 +447,7 @@
 }
 
 func (notExistError) Is(target error) bool {
-	return target == os.ErrNotExist
+	return target == fs.ErrNotExist
 }
 
 func (e notExistError) Unwrap() error {
diff --git a/src/cmd/go/internal/modfetch/sumdb.go b/src/cmd/go/internal/modfetch/sumdb.go
index 47a2571..5108961 100644
--- a/src/cmd/go/internal/modfetch/sumdb.go
+++ b/src/cmd/go/internal/modfetch/sumdb.go
@@ -12,6 +12,7 @@
 	"bytes"
 	"errors"
 	"fmt"
+	"io/fs"
 	"io/ioutil"
 	"net/url"
 	"os"
@@ -182,7 +183,7 @@
 			return nil
 		}
 	})
-	if errors.Is(err, os.ErrNotExist) {
+	if errors.Is(err, fs.ErrNotExist) {
 		// No proxies, or all proxies failed (with 404, 410, or were were allowed
 		// to fall back), or we reached an explicit "direct" or "off".
 		c.base = c.direct
@@ -203,7 +204,7 @@
 	}
 	targ := filepath.Join(cfg.SumdbDir, file)
 	data, err = lockedfile.Read(targ)
-	if errors.Is(err, os.ErrNotExist) {
+	if errors.Is(err, fs.ErrNotExist) {
 		// Treat non-existent as empty, to bootstrap the "latest" file
 		// the first time we connect to a given database.
 		return []byte{}, nil
@@ -257,7 +258,7 @@
 	// during which the empty file can be locked for reading.
 	// Treat observing an empty file as file not found.
 	if err == nil && len(data) == 0 {
-		err = &os.PathError{Op: "read", Path: targ, Err: os.ErrNotExist}
+		err = &fs.PathError{Op: "read", Path: targ, Err: fs.ErrNotExist}
 	}
 	return data, err
 }
diff --git a/src/cmd/go/internal/modload/import.go b/src/cmd/go/internal/modload/import.go
index 6d0d8de..bcbc9b0 100644
--- a/src/cmd/go/internal/modload/import.go
+++ b/src/cmd/go/internal/modload/import.go
@@ -10,6 +10,7 @@
 	"fmt"
 	"go/build"
 	"internal/goroot"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"sort"
@@ -347,7 +348,7 @@
 
 	candidates, err := QueryPattern(ctx, path, "latest", Selected, CheckAllowed)
 	if err != nil {
-		if errors.Is(err, os.ErrNotExist) {
+		if errors.Is(err, fs.ErrNotExist) {
 			// Return "cannot find module providing package […]" instead of whatever
 			// low-level error QueryPattern produced.
 			return module.Version{}, &ImportMissingError{Path: path, QueryErr: err}
diff --git a/src/cmd/go/internal/modload/load.go b/src/cmd/go/internal/modload/load.go
index 4ddb817..4b3ded8 100644
--- a/src/cmd/go/internal/modload/load.go
+++ b/src/cmd/go/internal/modload/load.go
@@ -98,6 +98,7 @@
 	"errors"
 	"fmt"
 	"go/build"
+	"io/fs"
 	"os"
 	"path"
 	pathpkg "path"
@@ -364,7 +365,7 @@
 			if os.IsNotExist(err) {
 				// Canonicalize OS-specific errors to errDirectoryNotFound so that error
 				// messages will be easier for users to search for.
-				return "", &os.PathError{Op: "stat", Path: absDir, Err: errDirectoryNotFound}
+				return "", &fs.PathError{Op: "stat", Path: absDir, Err: errDirectoryNotFound}
 			}
 			return "", err
 		}
diff --git a/src/cmd/go/internal/modload/query.go b/src/cmd/go/internal/modload/query.go
index 3b27e66..6b14768 100644
--- a/src/cmd/go/internal/modload/query.go
+++ b/src/cmd/go/internal/modload/query.go
@@ -8,6 +8,7 @@
 	"context"
 	"errors"
 	"fmt"
+	"io/fs"
 	"os"
 	pathpkg "path"
 	"path/filepath"
@@ -145,7 +146,7 @@
 			canonicalQuery := module.CanonicalVersion(query)
 			if canonicalQuery != "" && query != canonicalQuery {
 				info, err = repo.Stat(canonicalQuery)
-				if err != nil && !errors.Is(err, os.ErrNotExist) {
+				if err != nil && !errors.Is(err, fs.ErrNotExist) {
 					return info, err
 				}
 			}
@@ -230,7 +231,7 @@
 			if qm.allowsVersion(ctx, latest.Version) {
 				return lookup(latest.Version)
 			}
-		} else if !errors.Is(err, os.ErrNotExist) {
+		} else if !errors.Is(err, fs.ErrNotExist) {
 			return nil, err
 		}
 	}
@@ -701,7 +702,7 @@
 				noVersion = rErr
 			}
 		default:
-			if errors.Is(rErr, os.ErrNotExist) {
+			if errors.Is(rErr, fs.ErrNotExist) {
 				if notExistErr == nil {
 					notExistErr = rErr
 				}
@@ -744,7 +745,7 @@
 // A NoMatchingVersionError indicates that Query found a module at the requested
 // path, but not at any versions satisfying the query string and allow-function.
 //
-// NOTE: NoMatchingVersionError MUST NOT implement Is(os.ErrNotExist).
+// NOTE: NoMatchingVersionError MUST NOT implement Is(fs.ErrNotExist).
 //
 // If the module came from a proxy, that proxy had to return a successful status
 // code for the versions it knows about, and thus did not have the opportunity
@@ -765,7 +766,7 @@
 // module at the requested version, but that module did not contain any packages
 // matching the requested pattern.
 //
-// NOTE: PackageNotInModuleError MUST NOT implement Is(os.ErrNotExist).
+// NOTE: PackageNotInModuleError MUST NOT implement Is(fs.ErrNotExist).
 //
 // If the module came from a proxy, that proxy had to return a successful status
 // code for the versions it knows about, and thus did not have the opportunity
diff --git a/src/cmd/go/internal/modload/search.go b/src/cmd/go/internal/modload/search.go
index 0f82026..19289ce 100644
--- a/src/cmd/go/internal/modload/search.go
+++ b/src/cmd/go/internal/modload/search.go
@@ -7,6 +7,7 @@
 import (
 	"context"
 	"fmt"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"strings"
@@ -54,7 +55,7 @@
 
 	walkPkgs := func(root, importPathRoot string, prune pruning) {
 		root = filepath.Clean(root)
-		err := fsys.Walk(root, func(path string, fi os.FileInfo, err error) error {
+		err := fsys.Walk(root, func(path string, fi fs.FileInfo, err error) error {
 			if err != nil {
 				m.AddError(err)
 				return nil
@@ -85,7 +86,7 @@
 			}
 
 			if !fi.IsDir() {
-				if fi.Mode()&os.ModeSymlink != 0 && want {
+				if fi.Mode()&fs.ModeSymlink != 0 && want {
 					if target, err := os.Stat(path); err == nil && target.IsDir() {
 						fmt.Fprintf(os.Stderr, "warning: ignoring symlink %s\n", path)
 					}
diff --git a/src/cmd/go/internal/modload/stat_openfile.go b/src/cmd/go/internal/modload/stat_openfile.go
index 931aaf1..7cdeaf4 100644
--- a/src/cmd/go/internal/modload/stat_openfile.go
+++ b/src/cmd/go/internal/modload/stat_openfile.go
@@ -13,12 +13,13 @@
 package modload
 
 import (
+	"io/fs"
 	"os"
 )
 
 // hasWritePerm reports whether the current user has permission to write to the
 // file with the given info.
-func hasWritePerm(path string, _ os.FileInfo) bool {
+func hasWritePerm(path string, _ fs.FileInfo) bool {
 	if f, err := os.OpenFile(path, os.O_WRONLY, 0); err == nil {
 		f.Close()
 		return true
diff --git a/src/cmd/go/internal/modload/stat_unix.go b/src/cmd/go/internal/modload/stat_unix.go
index ea3b801f..6506844 100644
--- a/src/cmd/go/internal/modload/stat_unix.go
+++ b/src/cmd/go/internal/modload/stat_unix.go
@@ -7,6 +7,7 @@
 package modload
 
 import (
+	"io/fs"
 	"os"
 	"syscall"
 )
@@ -17,7 +18,7 @@
 // Although the root user on most Unix systems can write to files even without
 // permission, hasWritePerm reports false if no appropriate permission bit is
 // set even if the current user is root.
-func hasWritePerm(path string, fi os.FileInfo) bool {
+func hasWritePerm(path string, fi fs.FileInfo) bool {
 	if os.Getuid() == 0 {
 		// The root user can access any file, but we still want to default to
 		// read-only mode if the go.mod file is marked as globally non-writable.
diff --git a/src/cmd/go/internal/modload/stat_windows.go b/src/cmd/go/internal/modload/stat_windows.go
index d7826cf..0ac2391 100644
--- a/src/cmd/go/internal/modload/stat_windows.go
+++ b/src/cmd/go/internal/modload/stat_windows.go
@@ -6,13 +6,11 @@
 
 package modload
 
-import (
-	"os"
-)
+import "io/fs"
 
 // hasWritePerm reports whether the current user has permission to write to the
 // file with the given info.
-func hasWritePerm(_ string, fi os.FileInfo) bool {
+func hasWritePerm(_ string, fi fs.FileInfo) bool {
 	// Windows has a read-only attribute independent of ACLs, so use that to
 	// determine whether the file is intended to be overwritten.
 	//
diff --git a/src/cmd/go/internal/modload/vendor.go b/src/cmd/go/internal/modload/vendor.go
index 9f34b82..ab29d4d 100644
--- a/src/cmd/go/internal/modload/vendor.go
+++ b/src/cmd/go/internal/modload/vendor.go
@@ -7,8 +7,8 @@
 import (
 	"errors"
 	"fmt"
+	"io/fs"
 	"io/ioutil"
-	"os"
 	"path/filepath"
 	"strings"
 	"sync"
@@ -42,7 +42,7 @@
 		vendorMeta = make(map[module.Version]vendorMetadata)
 		data, err := ioutil.ReadFile(filepath.Join(ModRoot(), "vendor/modules.txt"))
 		if err != nil {
-			if !errors.Is(err, os.ErrNotExist) {
+			if !errors.Is(err, fs.ErrNotExist) {
 				base.Fatalf("go: %s", err)
 			}
 			return
diff --git a/src/cmd/go/internal/renameio/renameio.go b/src/cmd/go/internal/renameio/renameio.go
index d573cc6..60a7138 100644
--- a/src/cmd/go/internal/renameio/renameio.go
+++ b/src/cmd/go/internal/renameio/renameio.go
@@ -8,6 +8,7 @@
 import (
 	"bytes"
 	"io"
+	"io/fs"
 	"math/rand"
 	"os"
 	"path/filepath"
@@ -29,13 +30,13 @@
 // final name.
 //
 // That ensures that the final location, if it exists, is always a complete file.
-func WriteFile(filename string, data []byte, perm os.FileMode) (err error) {
+func WriteFile(filename string, data []byte, perm fs.FileMode) (err error) {
 	return WriteToFile(filename, bytes.NewReader(data), perm)
 }
 
 // WriteToFile is a variant of WriteFile that accepts the data as an io.Reader
 // instead of a slice.
-func WriteToFile(filename string, data io.Reader, perm os.FileMode) (err error) {
+func WriteToFile(filename string, data io.Reader, perm fs.FileMode) (err error) {
 	f, err := tempFile(filepath.Dir(filename), filepath.Base(filename), perm)
 	if err != nil {
 		return err
@@ -80,7 +81,7 @@
 }
 
 // tempFile creates a new temporary file with given permission bits.
-func tempFile(dir, prefix string, perm os.FileMode) (f *os.File, err error) {
+func tempFile(dir, prefix string, perm fs.FileMode) (f *os.File, err error) {
 	for i := 0; i < 10000; i++ {
 		name := filepath.Join(dir, prefix+strconv.Itoa(rand.Intn(1000000000))+patternSuffix)
 		f, err = os.OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, perm)
diff --git a/src/cmd/go/internal/renameio/umask_test.go b/src/cmd/go/internal/renameio/umask_test.go
index d75d67c..19e217c 100644
--- a/src/cmd/go/internal/renameio/umask_test.go
+++ b/src/cmd/go/internal/renameio/umask_test.go
@@ -7,6 +7,7 @@
 package renameio
 
 import (
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -36,7 +37,7 @@
 		t.Fatalf("Stat %q (looking for mode %#o): %s", file, mode, err)
 	}
 
-	if fi.Mode()&os.ModePerm != 0640 {
-		t.Errorf("Stat %q: mode %#o want %#o", file, fi.Mode()&os.ModePerm, 0640)
+	if fi.Mode()&fs.ModePerm != 0640 {
+		t.Errorf("Stat %q: mode %#o want %#o", file, fi.Mode()&fs.ModePerm, 0640)
 	}
 }
diff --git a/src/cmd/go/internal/search/search.go b/src/cmd/go/internal/search/search.go
index b1d2a93..e4784e9 100644
--- a/src/cmd/go/internal/search/search.go
+++ b/src/cmd/go/internal/search/search.go
@@ -10,6 +10,7 @@
 	"cmd/go/internal/fsys"
 	"fmt"
 	"go/build"
+	"io/fs"
 	"os"
 	"path"
 	"path/filepath"
@@ -128,7 +129,7 @@
 		if m.pattern == "cmd" {
 			root += "cmd" + string(filepath.Separator)
 		}
-		err := fsys.Walk(root, func(path string, fi os.FileInfo, err error) error {
+		err := fsys.Walk(root, func(path string, fi fs.FileInfo, err error) error {
 			if err != nil {
 				return err // Likely a permission error, which could interfere with matching.
 			}
@@ -154,7 +155,7 @@
 			}
 
 			if !fi.IsDir() {
-				if fi.Mode()&os.ModeSymlink != 0 && want {
+				if fi.Mode()&fs.ModeSymlink != 0 && want {
 					if target, err := os.Stat(path); err == nil && target.IsDir() {
 						fmt.Fprintf(os.Stderr, "warning: ignoring symlink %s\n", path)
 					}
@@ -264,7 +265,7 @@
 		}
 	}
 
-	err := fsys.Walk(dir, func(path string, fi os.FileInfo, err error) error {
+	err := fsys.Walk(dir, func(path string, fi fs.FileInfo, err error) error {
 		if err != nil {
 			return err // Likely a permission error, which could interfere with matching.
 		}
diff --git a/src/cmd/go/internal/test/test.go b/src/cmd/go/internal/test/test.go
index 51d333d..00da977 100644
--- a/src/cmd/go/internal/test/test.go
+++ b/src/cmd/go/internal/test/test.go
@@ -12,6 +12,7 @@
 	"fmt"
 	"go/build"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -1598,7 +1599,7 @@
 	return h.Sum()
 }
 
-func hashWriteStat(h io.Writer, info os.FileInfo) {
+func hashWriteStat(h io.Writer, info fs.FileInfo) {
 	fmt.Fprintf(h, "stat %d %x %v %v\n", info.Size(), uint64(info.Mode()), info.ModTime(), info.IsDir())
 }
 
diff --git a/src/cmd/go/internal/vcs/vcs.go b/src/cmd/go/internal/vcs/vcs.go
index 90bf102..7812afd 100644
--- a/src/cmd/go/internal/vcs/vcs.go
+++ b/src/cmd/go/internal/vcs/vcs.go
@@ -10,6 +10,7 @@
 	"fmt"
 	"internal/lazyregexp"
 	"internal/singleflight"
+	"io/fs"
 	"log"
 	urlpkg "net/url"
 	"os"
@@ -404,9 +405,9 @@
 	if len(args) >= 2 && args[0] == "-go-internal-mkdir" {
 		var err error
 		if filepath.IsAbs(args[1]) {
-			err = os.Mkdir(args[1], os.ModePerm)
+			err = os.Mkdir(args[1], fs.ModePerm)
 		} else {
-			err = os.Mkdir(filepath.Join(dir, args[1]), os.ModePerm)
+			err = os.Mkdir(filepath.Join(dir, args[1]), fs.ModePerm)
 		}
 		if err != nil {
 			return nil, err
diff --git a/src/cmd/go/internal/version/version.go b/src/cmd/go/internal/version/version.go
index 5aa0f8e..44ac24c 100644
--- a/src/cmd/go/internal/version/version.go
+++ b/src/cmd/go/internal/version/version.go
@@ -10,6 +10,7 @@
 	"context"
 	"encoding/binary"
 	"fmt"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -87,8 +88,8 @@
 
 // scanDir scans a directory for executables to run scanFile on.
 func scanDir(dir string) {
-	filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
-		if info.Mode().IsRegular() || info.Mode()&os.ModeSymlink != 0 {
+	filepath.Walk(dir, func(path string, info fs.FileInfo, err error) error {
+		if info.Mode().IsRegular() || info.Mode()&fs.ModeSymlink != 0 {
 			scanFile(path, info, *versionV)
 		}
 		return nil
@@ -96,7 +97,7 @@
 }
 
 // isExe reports whether the file should be considered executable.
-func isExe(file string, info os.FileInfo) bool {
+func isExe(file string, info fs.FileInfo) bool {
 	if runtime.GOOS == "windows" {
 		return strings.HasSuffix(strings.ToLower(file), ".exe")
 	}
@@ -107,8 +108,8 @@
 // If mustPrint is true, scanFile will report any error reading file.
 // Otherwise (mustPrint is false, because scanFile is being called
 // by scanDir) scanFile prints nothing for non-Go executables.
-func scanFile(file string, info os.FileInfo, mustPrint bool) {
-	if info.Mode()&os.ModeSymlink != 0 {
+func scanFile(file string, info fs.FileInfo, mustPrint bool) {
+	if info.Mode()&fs.ModeSymlink != 0 {
 		// Accept file symlinks only.
 		i, err := os.Stat(file)
 		if err != nil || !i.Mode().IsRegular() {
diff --git a/src/cmd/go/internal/web/api.go b/src/cmd/go/internal/web/api.go
index 5708188..f7d3ed6 100644
--- a/src/cmd/go/internal/web/api.go
+++ b/src/cmd/go/internal/web/api.go
@@ -13,9 +13,9 @@
 	"bytes"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"net/url"
-	"os"
 	"strings"
 	"unicode"
 	"unicode/utf8"
@@ -56,7 +56,7 @@
 	}
 
 	if err := e.Err; err != nil {
-		if pErr, ok := e.Err.(*os.PathError); ok && strings.HasSuffix(e.URL, pErr.Path) {
+		if pErr, ok := e.Err.(*fs.PathError); ok && strings.HasSuffix(e.URL, pErr.Path) {
 			// Remove the redundant copy of the path.
 			err = pErr.Err
 		}
@@ -67,7 +67,7 @@
 }
 
 func (e *HTTPError) Is(target error) bool {
-	return target == os.ErrNotExist && (e.StatusCode == 404 || e.StatusCode == 410)
+	return target == fs.ErrNotExist && (e.StatusCode == 404 || e.StatusCode == 410)
 }
 
 func (e *HTTPError) Unwrap() error {
diff --git a/src/cmd/go/internal/web/file_test.go b/src/cmd/go/internal/web/file_test.go
index 6339469..a1bb080 100644
--- a/src/cmd/go/internal/web/file_test.go
+++ b/src/cmd/go/internal/web/file_test.go
@@ -6,6 +6,7 @@
 
 import (
 	"errors"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -54,7 +55,7 @@
 	}
 
 	b, err := GetBytes(u)
-	if !errors.Is(err, os.ErrNotExist) {
-		t.Fatalf("GetBytes(%v) = %q, %v; want _, os.ErrNotExist", u, b, err)
+	if !errors.Is(err, fs.ErrNotExist) {
+		t.Fatalf("GetBytes(%v) = %q, %v; want _, fs.ErrNotExist", u, b, err)
 	}
 }
diff --git a/src/cmd/go/internal/work/build_test.go b/src/cmd/go/internal/work/build_test.go
index 904aee0..e941729 100644
--- a/src/cmd/go/internal/work/build_test.go
+++ b/src/cmd/go/internal/work/build_test.go
@@ -7,6 +7,7 @@
 import (
 	"bytes"
 	"fmt"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -253,7 +254,7 @@
 	}
 
 	// Change setgiddir's permissions to include the SetGID bit.
-	if err := os.Chmod(setgiddir, 0755|os.ModeSetgid); err != nil {
+	if err := os.Chmod(setgiddir, 0755|fs.ModeSetgid); err != nil {
 		t.Fatal(err)
 	}
 
diff --git a/src/cmd/go/internal/work/exec.go b/src/cmd/go/internal/work/exec.go
index 824a4b5..717b0cc 100644
--- a/src/cmd/go/internal/work/exec.go
+++ b/src/cmd/go/internal/work/exec.go
@@ -14,6 +14,7 @@
 	"fmt"
 	"internal/lazyregexp"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"log"
 	"math/rand"
@@ -1560,7 +1561,7 @@
 		return err
 	}
 
-	perm := os.FileMode(0666)
+	perm := fs.FileMode(0666)
 	if a1.Mode == "link" {
 		switch cfg.BuildBuildmode {
 		case "c-archive", "c-shared", "plugin":
@@ -1609,7 +1610,7 @@
 }
 
 // moveOrCopyFile is like 'mv src dst' or 'cp src dst'.
-func (b *Builder) moveOrCopyFile(dst, src string, perm os.FileMode, force bool) error {
+func (b *Builder) moveOrCopyFile(dst, src string, perm fs.FileMode, force bool) error {
 	if cfg.BuildN {
 		b.Showcmd("", "mv %s %s", src, dst)
 		return nil
@@ -1635,7 +1636,7 @@
 	// we have to copy the file to retain the correct permissions.
 	// https://golang.org/issue/18878
 	if fi, err := os.Stat(filepath.Dir(dst)); err == nil {
-		if fi.IsDir() && (fi.Mode()&os.ModeSetgid) != 0 {
+		if fi.IsDir() && (fi.Mode()&fs.ModeSetgid) != 0 {
 			return b.copyFile(dst, src, perm, force)
 		}
 	}
@@ -1670,7 +1671,7 @@
 }
 
 // copyFile is like 'cp src dst'.
-func (b *Builder) copyFile(dst, src string, perm os.FileMode, force bool) error {
+func (b *Builder) copyFile(dst, src string, perm fs.FileMode, force bool) error {
 	if cfg.BuildN || cfg.BuildX {
 		b.Showcmd("", "cp %s %s", src, dst)
 		if cfg.BuildN {
diff --git a/src/cmd/go/proxy_test.go b/src/cmd/go/proxy_test.go
index 42972f5..8b0dbb7 100644
--- a/src/cmd/go/proxy_test.go
+++ b/src/cmd/go/proxy_test.go
@@ -12,6 +12,7 @@
 	"flag"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"log"
 	"net"
@@ -335,7 +336,7 @@
 		if testing.Verbose() {
 			fmt.Fprintf(os.Stderr, "go proxy: no archive %s %s: %v\n", path, vers, err)
 		}
-		if errors.Is(err, os.ErrNotExist) {
+		if errors.Is(err, fs.ErrNotExist) {
 			http.NotFound(w, r)
 		} else {
 			http.Error(w, "cannot load archive", 500)
@@ -443,7 +444,7 @@
 		return a
 	}).(*txtar.Archive)
 	if a == nil {
-		return nil, os.ErrNotExist
+		return nil, fs.ErrNotExist
 	}
 	return a, nil
 }
diff --git a/src/cmd/go/script_test.go b/src/cmd/go/script_test.go
index 9866462..a31561c 100644
--- a/src/cmd/go/script_test.go
+++ b/src/cmd/go/script_test.go
@@ -14,6 +14,7 @@
 	"fmt"
 	"go/build"
 	"internal/testenv"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -500,7 +501,7 @@
 		ts.fatalf("usage: chmod perm paths...")
 	}
 	perm, err := strconv.ParseUint(args[0], 0, 32)
-	if err != nil || perm&uint64(os.ModePerm) != perm {
+	if err != nil || perm&uint64(fs.ModePerm) != perm {
 		ts.fatalf("invalid mode: %s", args[0])
 	}
 	for _, arg := range args[1:] {
@@ -508,7 +509,7 @@
 		if !filepath.IsAbs(path) {
 			path = filepath.Join(ts.cd, arg)
 		}
-		err := os.Chmod(path, os.FileMode(perm))
+		err := os.Chmod(path, fs.FileMode(perm))
 		ts.check(err)
 	}
 }
@@ -595,7 +596,7 @@
 		var (
 			src  string
 			data []byte
-			mode os.FileMode
+			mode fs.FileMode
 		)
 		switch arg {
 		case "stdout":
diff --git a/src/cmd/go/testdata/addmod.go b/src/cmd/go/testdata/addmod.go
index d9c3aab..d1b6467 100644
--- a/src/cmd/go/testdata/addmod.go
+++ b/src/cmd/go/testdata/addmod.go
@@ -22,6 +22,7 @@
 	"bytes"
 	"flag"
 	"fmt"
+	"io/fs"
 	"io/ioutil"
 	"log"
 	"os"
@@ -121,7 +122,7 @@
 			{Name: ".info", Data: info},
 		}
 		dir = filepath.Clean(dir)
-		err = filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
+		err = filepath.Walk(dir, func(path string, info fs.FileInfo, err error) error {
 			if !info.Mode().IsRegular() {
 				return nil
 			}
diff --git a/src/cmd/go/testdata/savedir.go b/src/cmd/go/testdata/savedir.go
index 48a6318..04902df 100644
--- a/src/cmd/go/testdata/savedir.go
+++ b/src/cmd/go/testdata/savedir.go
@@ -17,6 +17,7 @@
 import (
 	"flag"
 	"fmt"
+	"io/fs"
 	"io/ioutil"
 	"log"
 	"os"
@@ -48,7 +49,7 @@
 
 	a := new(txtar.Archive)
 	dir = filepath.Clean(dir)
-	filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
+	filepath.Walk(dir, func(path string, info fs.FileInfo, err error) error {
 		if path == dir {
 			return nil
 		}
diff --git a/src/cmd/gofmt/gofmt.go b/src/cmd/gofmt/gofmt.go
index 8c56af7..48b6ad6 100644
--- a/src/cmd/gofmt/gofmt.go
+++ b/src/cmd/gofmt/gofmt.go
@@ -14,6 +14,7 @@
 	"go/scanner"
 	"go/token"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -73,7 +74,7 @@
 	}
 }
 
-func isGoFile(f os.FileInfo) bool {
+func isGoFile(f fs.FileInfo) bool {
 	// ignore non-Go files
 	name := f.Name()
 	return !f.IsDir() && !strings.HasPrefix(name, ".") && strings.HasSuffix(name, ".go")
@@ -81,7 +82,7 @@
 
 // If in == nil, the source is the contents of the file with the given filename.
 func processFile(filename string, in io.Reader, out io.Writer, stdin bool) error {
-	var perm os.FileMode = 0644
+	var perm fs.FileMode = 0644
 	if in == nil {
 		f, err := os.Open(filename)
 		if err != nil {
@@ -163,7 +164,7 @@
 	return err
 }
 
-func visitFile(path string, f os.FileInfo, err error) error {
+func visitFile(path string, f fs.FileInfo, err error) error {
 	if err == nil && isGoFile(f) {
 		err = processFile(path, nil, os.Stdout, false)
 	}
@@ -275,7 +276,7 @@
 // backupFile writes data to a new file named filename<number> with permissions perm,
 // with <number randomly chosen such that the file name is unique. backupFile returns
 // the chosen file name.
-func backupFile(filename string, data []byte, perm os.FileMode) (string, error) {
+func backupFile(filename string, data []byte, perm fs.FileMode) (string, error) {
 	// create backup file
 	f, err := ioutil.TempFile(filepath.Dir(filename), filepath.Base(filename))
 	if err != nil {
diff --git a/src/cmd/gofmt/long_test.go b/src/cmd/gofmt/long_test.go
index e2a6208..28306ce 100644
--- a/src/cmd/gofmt/long_test.go
+++ b/src/cmd/gofmt/long_test.go
@@ -16,6 +16,7 @@
 	"go/printer"
 	"go/token"
 	"io"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -107,7 +108,7 @@
 func genFilenames(t *testing.T, filenames chan<- string) {
 	defer close(filenames)
 
-	handleFile := func(filename string, fi os.FileInfo, err error) error {
+	handleFile := func(filename string, fi fs.FileInfo, err error) error {
 		if err != nil {
 			t.Error(err)
 			return nil
diff --git a/src/cmd/internal/buildid/buildid.go b/src/cmd/internal/buildid/buildid.go
index ac238d7..1d6563c 100644
--- a/src/cmd/internal/buildid/buildid.go
+++ b/src/cmd/internal/buildid/buildid.go
@@ -10,6 +10,7 @@
 	"fmt"
 	"internal/xcoff"
 	"io"
+	"io/fs"
 	"os"
 	"strconv"
 	"strings"
@@ -109,7 +110,7 @@
 // in cmd/go/internal/work/exec.go.
 func readGccgoArchive(name string, f *os.File) (string, error) {
 	bad := func() (string, error) {
-		return "", &os.PathError{Op: "parse", Path: name, Err: errBuildIDMalformed}
+		return "", &fs.PathError{Op: "parse", Path: name, Err: errBuildIDMalformed}
 	}
 
 	off := int64(8)
@@ -167,7 +168,7 @@
 // in cmd/go/internal/work/exec.go.
 func readGccgoBigArchive(name string, f *os.File) (string, error) {
 	bad := func() (string, error) {
-		return "", &os.PathError{Op: "parse", Path: name, Err: errBuildIDMalformed}
+		return "", &fs.PathError{Op: "parse", Path: name, Err: errBuildIDMalformed}
 	}
 
 	// Read fixed-length header.
@@ -309,13 +310,13 @@
 
 	j := bytes.Index(data[i+len(goBuildPrefix):], goBuildEnd)
 	if j < 0 {
-		return "", &os.PathError{Op: "parse", Path: name, Err: errBuildIDMalformed}
+		return "", &fs.PathError{Op: "parse", Path: name, Err: errBuildIDMalformed}
 	}
 
 	quoted := data[i+len(goBuildPrefix)-1 : i+len(goBuildPrefix)+j+1]
 	id, err = strconv.Unquote(string(quoted))
 	if err != nil {
-		return "", &os.PathError{Op: "parse", Path: name, Err: errBuildIDMalformed}
+		return "", &fs.PathError{Op: "parse", Path: name, Err: errBuildIDMalformed}
 	}
 	return id, nil
 }
diff --git a/src/cmd/internal/buildid/note.go b/src/cmd/internal/buildid/note.go
index 2d26ea9..f5b6fc5 100644
--- a/src/cmd/internal/buildid/note.go
+++ b/src/cmd/internal/buildid/note.go
@@ -11,6 +11,7 @@
 	"encoding/binary"
 	"fmt"
 	"io"
+	"io/fs"
 	"os"
 )
 
@@ -96,7 +97,7 @@
 
 	ef, err := elf.NewFile(bytes.NewReader(data))
 	if err != nil {
-		return "", &os.PathError{Path: name, Op: "parse", Err: err}
+		return "", &fs.PathError{Path: name, Op: "parse", Err: err}
 	}
 	var gnu string
 	for _, p := range ef.Progs {
@@ -181,13 +182,13 @@
 
 	mf, err := macho.NewFile(f)
 	if err != nil {
-		return "", &os.PathError{Path: name, Op: "parse", Err: err}
+		return "", &fs.PathError{Path: name, Op: "parse", Err: err}
 	}
 
 	sect := mf.Section("__text")
 	if sect == nil {
 		// Every binary has a __text section. Something is wrong.
-		return "", &os.PathError{Path: name, Op: "parse", Err: fmt.Errorf("cannot find __text section")}
+		return "", &fs.PathError{Path: name, Op: "parse", Err: fmt.Errorf("cannot find __text section")}
 	}
 
 	// It should be in the first few bytes, but read a lot just in case,
diff --git a/src/cmd/internal/moddeps/moddeps_test.go b/src/cmd/internal/moddeps/moddeps_test.go
index 2e61673..7362e78 100644
--- a/src/cmd/internal/moddeps/moddeps_test.go
+++ b/src/cmd/internal/moddeps/moddeps_test.go
@@ -8,6 +8,7 @@
 	"encoding/json"
 	"fmt"
 	"internal/testenv"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -32,7 +33,7 @@
 	goBin := testenv.GoToolPath(t)
 
 	goroot.once.Do(func() {
-		goroot.err = filepath.Walk(runtime.GOROOT(), func(path string, info os.FileInfo, err error) error {
+		goroot.err = filepath.Walk(runtime.GOROOT(), func(path string, info fs.FileInfo, err error) error {
 			if err != nil {
 				return err
 			}
diff --git a/src/cmd/pack/pack.go b/src/cmd/pack/pack.go
index c4e116b..82546ea 100644
--- a/src/cmd/pack/pack.go
+++ b/src/cmd/pack/pack.go
@@ -8,6 +8,7 @@
 	"cmd/internal/archive"
 	"fmt"
 	"io"
+	"io/fs"
 	"log"
 	"os"
 	"path/filepath"
@@ -221,7 +222,7 @@
 // FileLike abstracts the few methods we need, so we can test without needing real files.
 type FileLike interface {
 	Name() string
-	Stat() (os.FileInfo, error)
+	Stat() (fs.FileInfo, error)
 	Read([]byte) (int, error)
 	Close() error
 }
diff --git a/src/cmd/pack/pack_test.go b/src/cmd/pack/pack_test.go
index 2108330..9f65705 100644
--- a/src/cmd/pack/pack_test.go
+++ b/src/cmd/pack/pack_test.go
@@ -11,6 +11,7 @@
 	"fmt"
 	"internal/testenv"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -327,11 +328,11 @@
 	mode:     0644,
 }
 
-// FakeFile implements FileLike and also os.FileInfo.
+// FakeFile implements FileLike and also fs.FileInfo.
 type FakeFile struct {
 	name     string
 	contents string
-	mode     os.FileMode
+	mode     fs.FileMode
 	offset   int
 }
 
@@ -348,7 +349,7 @@
 	return f.name
 }
 
-func (f *FakeFile) Stat() (os.FileInfo, error) {
+func (f *FakeFile) Stat() (fs.FileInfo, error) {
 	return f, nil
 }
 
@@ -365,13 +366,13 @@
 	return nil
 }
 
-// os.FileInfo methods.
+// fs.FileInfo methods.
 
 func (f *FakeFile) Size() int64 {
 	return int64(len(f.contents))
 }
 
-func (f *FakeFile) Mode() os.FileMode {
+func (f *FakeFile) Mode() fs.FileMode {
 	return f.mode
 }
 
diff --git a/src/compress/gzip/issue14937_test.go b/src/compress/gzip/issue14937_test.go
index 7a19672..24db364 100644
--- a/src/compress/gzip/issue14937_test.go
+++ b/src/compress/gzip/issue14937_test.go
@@ -2,6 +2,7 @@
 
 import (
 	"internal/testenv"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -30,7 +31,7 @@
 		t.Fatal("error evaluating GOROOT: ", err)
 	}
 	var files []string
-	err = filepath.Walk(goroot, func(path string, info os.FileInfo, err error) error {
+	err = filepath.Walk(goroot, func(path string, info fs.FileInfo, err error) error {
 		if err != nil {
 			return err
 		}
diff --git a/src/crypto/rand/eagain.go b/src/crypto/rand/eagain.go
index f251ba2..c949971 100644
--- a/src/crypto/rand/eagain.go
+++ b/src/crypto/rand/eagain.go
@@ -7,7 +7,7 @@
 package rand
 
 import (
-	"os"
+	"io/fs"
 	"syscall"
 )
 
@@ -18,7 +18,7 @@
 // unixIsEAGAIN reports whether err is a syscall.EAGAIN wrapped in a PathError.
 // See golang.org/issue/9205
 func unixIsEAGAIN(err error) bool {
-	if pe, ok := err.(*os.PathError); ok {
+	if pe, ok := err.(*fs.PathError); ok {
 		if errno, ok := pe.Err.(syscall.Errno); ok && errno == syscall.EAGAIN {
 			return true
 		}
diff --git a/src/crypto/x509/root_unix.go b/src/crypto/x509/root_unix.go
index 2aa3875..ae72f02 100644
--- a/src/crypto/x509/root_unix.go
+++ b/src/crypto/x509/root_unix.go
@@ -7,6 +7,7 @@
 package x509
 
 import (
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -83,7 +84,7 @@
 
 // readUniqueDirectoryEntries is like ioutil.ReadDir but omits
 // symlinks that point within the directory.
-func readUniqueDirectoryEntries(dir string) ([]os.FileInfo, error) {
+func readUniqueDirectoryEntries(dir string) ([]fs.FileInfo, error) {
 	fis, err := ioutil.ReadDir(dir)
 	if err != nil {
 		return nil, err
@@ -99,8 +100,8 @@
 
 // isSameDirSymlink reports whether fi in dir is a symlink with a
 // target not containing a slash.
-func isSameDirSymlink(fi os.FileInfo, dir string) bool {
-	if fi.Mode()&os.ModeSymlink == 0 {
+func isSameDirSymlink(fi fs.FileInfo, dir string) bool {
+	if fi.Mode()&fs.ModeSymlink == 0 {
 		return false
 	}
 	target, err := os.Readlink(filepath.Join(dir, fi.Name()))
diff --git a/src/errors/errors.go b/src/errors/errors.go
index d923ad4..f2fabac 100644
--- a/src/errors/errors.go
+++ b/src/errors/errors.go
@@ -27,30 +27,30 @@
 // second. It reports whether it finds a match. It should be used in preference to
 // simple equality checks:
 //
-//	if errors.Is(err, os.ErrExist)
+//	if errors.Is(err, fs.ErrExist)
 //
 // is preferable to
 //
-//	if err == os.ErrExist
+//	if err == fs.ErrExist
 //
-// because the former will succeed if err wraps os.ErrExist.
+// because the former will succeed if err wraps fs.ErrExist.
 //
 // As unwraps its first argument sequentially looking for an error that can be
 // assigned to its second argument, which must be a pointer. If it succeeds, it
 // performs the assignment and returns true. Otherwise, it returns false. The form
 //
-//	var perr *os.PathError
+//	var perr *fs.PathError
 //	if errors.As(err, &perr) {
 //		fmt.Println(perr.Path)
 //	}
 //
 // is preferable to
 //
-//	if perr, ok := err.(*os.PathError); ok {
+//	if perr, ok := err.(*fs.PathError); ok {
 //		fmt.Println(perr.Path)
 //	}
 //
-// because the former will succeed if err wraps an *os.PathError.
+// because the former will succeed if err wraps an *fs.PathError.
 package errors
 
 // New returns an error that formats as the given text.
diff --git a/src/errors/wrap.go b/src/errors/wrap.go
index b82ca34..7928fe6 100644
--- a/src/errors/wrap.go
+++ b/src/errors/wrap.go
@@ -32,9 +32,9 @@
 // An error type might provide an Is method so it can be treated as equivalent
 // to an existing error. For example, if MyError defines
 //
-//	func (m MyError) Is(target error) bool { return target == os.ErrExist }
+//	func (m MyError) Is(target error) bool { return target == fs.ErrExist }
 //
-// then Is(MyError{}, os.ErrExist) returns true. See syscall.Errno.Is for
+// then Is(MyError{}, fs.ErrExist) returns true. See syscall.Errno.Is for
 // an example in the standard library.
 func Is(err, target error) bool {
 	if target == nil {
diff --git a/src/errors/wrap_test.go b/src/errors/wrap_test.go
index 4a4a732..6f66e99 100644
--- a/src/errors/wrap_test.go
+++ b/src/errors/wrap_test.go
@@ -7,6 +7,7 @@
 import (
 	"errors"
 	"fmt"
+	"io/fs"
 	"os"
 	"reflect"
 	"testing"
@@ -61,7 +62,7 @@
 	f   func(error) bool
 }
 
-var poserPathErr = &os.PathError{Op: "poser"}
+var poserPathErr = &fs.PathError{Op: "poser"}
 
 func (p *poser) Error() string     { return p.msg }
 func (p *poser) Is(err error) bool { return p.f(err) }
@@ -71,7 +72,7 @@
 		*x = p
 	case *errorT:
 		*x = errorT{"poser"}
-	case **os.PathError:
+	case **fs.PathError:
 		*x = poserPathErr
 	default:
 		return false
@@ -81,7 +82,7 @@
 
 func TestAs(t *testing.T) {
 	var errT errorT
-	var errP *os.PathError
+	var errP *fs.PathError
 	var timeout interface{ Timeout() bool }
 	var p *poser
 	_, errF := os.Open("non-existing")
@@ -240,7 +241,7 @@
 
 func ExampleIs() {
 	if _, err := os.Open("non-existing"); err != nil {
-		if errors.Is(err, os.ErrNotExist) {
+		if errors.Is(err, fs.ErrNotExist) {
 			fmt.Println("file does not exist")
 		} else {
 			fmt.Println(err)
@@ -253,7 +254,7 @@
 
 func ExampleAs() {
 	if _, err := os.Open("non-existing"); err != nil {
-		var pathError *os.PathError
+		var pathError *fs.PathError
 		if errors.As(err, &pathError) {
 			fmt.Println("Failed at path:", pathError.Path)
 		} else {
diff --git a/src/go/build/build.go b/src/go/build/build.go
index 7a96680..6141f4a 100644
--- a/src/go/build/build.go
+++ b/src/go/build/build.go
@@ -15,6 +15,7 @@
 	"internal/goroot"
 	"internal/goversion"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -98,10 +99,10 @@
 	// filepath.EvalSymlinks.
 	HasSubdir func(root, dir string) (rel string, ok bool)
 
-	// ReadDir returns a slice of os.FileInfo, sorted by Name,
+	// ReadDir returns a slice of fs.FileInfo, sorted by Name,
 	// describing the content of the named directory.
 	// If ReadDir is nil, Import uses ioutil.ReadDir.
-	ReadDir func(dir string) ([]os.FileInfo, error)
+	ReadDir func(dir string) ([]fs.FileInfo, error)
 
 	// OpenFile opens a file (not a directory) for reading.
 	// If OpenFile is nil, Import uses os.Open.
@@ -183,7 +184,7 @@
 }
 
 // readDir calls ctxt.ReadDir (if not nil) or else ioutil.ReadDir.
-func (ctxt *Context) readDir(path string) ([]os.FileInfo, error) {
+func (ctxt *Context) readDir(path string) ([]fs.FileInfo, error) {
 	if f := ctxt.ReadDir; f != nil {
 		return f(path)
 	}
@@ -794,7 +795,7 @@
 		if d.IsDir() {
 			continue
 		}
-		if (d.Mode() & os.ModeSymlink) != 0 {
+		if d.Mode()&fs.ModeSymlink != 0 {
 			if fi, err := os.Stat(filepath.Join(p.Dir, d.Name())); err == nil && fi.IsDir() {
 				// Symlinks to directories are not source files.
 				continue
diff --git a/src/go/build/deps_test.go b/src/go/build/deps_test.go
index 96e239a..9e72c8f 100644
--- a/src/go/build/deps_test.go
+++ b/src/go/build/deps_test.go
@@ -11,6 +11,7 @@
 	"bytes"
 	"fmt"
 	"internal/testenv"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -500,7 +501,7 @@
 	var pkgs []string
 
 	src := filepath.Join(goroot, "src") + string(filepath.Separator)
-	walkFn := func(path string, fi os.FileInfo, err error) error {
+	walkFn := func(path string, fi fs.FileInfo, err error) error {
 		if err != nil || !fi.IsDir() || path == src {
 			return nil
 		}
diff --git a/src/go/doc/doc_test.go b/src/go/doc/doc_test.go
index f1e612c..ab98bed 100644
--- a/src/go/doc/doc_test.go
+++ b/src/go/doc/doc_test.go
@@ -12,8 +12,8 @@
 	"go/parser"
 	"go/printer"
 	"go/token"
+	"io/fs"
 	"io/ioutil"
-	"os"
 	"path/filepath"
 	"regexp"
 	"strings"
@@ -66,7 +66,7 @@
 	return indent + strings.ReplaceAll(s, "\n", "\n"+indent) + end
 }
 
-func isGoFile(fi os.FileInfo) bool {
+func isGoFile(fi fs.FileInfo) bool {
 	name := fi.Name()
 	return !fi.IsDir() &&
 		len(name) > 0 && name[0] != '.' && // ignore .files
@@ -86,7 +86,7 @@
 		if err != nil {
 			t.Fatal(err)
 		}
-		filter = func(fi os.FileInfo) bool {
+		filter = func(fi fs.FileInfo) bool {
 			return isGoFile(fi) && rx.MatchString(fi.Name())
 		}
 	}
diff --git a/src/go/doc/headscan.go b/src/go/doc/headscan.go
index 3f782cc..8ea4623 100644
--- a/src/go/doc/headscan.go
+++ b/src/go/doc/headscan.go
@@ -23,6 +23,7 @@
 	"go/parser"
 	"go/token"
 	"internal/lazyregexp"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -39,7 +40,7 @@
 
 const html_endh = "</h3>\n"
 
-func isGoFile(fi os.FileInfo) bool {
+func isGoFile(fi fs.FileInfo) bool {
 	return strings.HasSuffix(fi.Name(), ".go") &&
 		!strings.HasSuffix(fi.Name(), "_test.go")
 }
@@ -68,7 +69,7 @@
 	flag.Parse()
 	fset := token.NewFileSet()
 	nheadings := 0
-	err := filepath.Walk(*root, func(path string, fi os.FileInfo, err error) error {
+	err := filepath.Walk(*root, func(path string, fi fs.FileInfo, err error) error {
 		if !fi.IsDir() {
 			return nil
 		}
diff --git a/src/go/parser/interface.go b/src/go/parser/interface.go
index 54f9d7b..b2d834f 100644
--- a/src/go/parser/interface.go
+++ b/src/go/parser/interface.go
@@ -12,8 +12,8 @@
 	"go/ast"
 	"go/token"
 	"io"
+	"io/fs"
 	"io/ioutil"
-	"os"
 	"path/filepath"
 	"strings"
 )
@@ -123,7 +123,7 @@
 // directory specified by path and returns a map of package name -> package
 // AST with all the packages found.
 //
-// If filter != nil, only the files with os.FileInfo entries passing through
+// If filter != nil, only the files with fs.FileInfo entries passing through
 // the filter (and ending in ".go") are considered. The mode bits are passed
 // to ParseFile unchanged. Position information is recorded in fset, which
 // must not be nil.
@@ -132,7 +132,7 @@
 // returned. If a parse error occurred, a non-nil but incomplete map and the
 // first error encountered are returned.
 //
-func ParseDir(fset *token.FileSet, path string, filter func(os.FileInfo) bool, mode Mode) (pkgs map[string]*ast.Package, first error) {
+func ParseDir(fset *token.FileSet, path string, filter func(fs.FileInfo) bool, mode Mode) (pkgs map[string]*ast.Package, first error) {
 	list, err := ioutil.ReadDir(path)
 	if err != nil {
 		return nil, err
diff --git a/src/go/parser/parser_test.go b/src/go/parser/parser_test.go
index 25a374e..7193a32 100644
--- a/src/go/parser/parser_test.go
+++ b/src/go/parser/parser_test.go
@@ -9,7 +9,7 @@
 	"fmt"
 	"go/ast"
 	"go/token"
-	"os"
+	"io/fs"
 	"strings"
 	"testing"
 )
@@ -40,7 +40,7 @@
 	return false
 }
 
-func dirFilter(f os.FileInfo) bool { return nameFilter(f.Name()) }
+func dirFilter(f fs.FileInfo) bool { return nameFilter(f.Name()) }
 
 func TestParseFile(t *testing.T) {
 	src := "package p\nvar _=s[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]+\ns[::]"
diff --git a/src/index/suffixarray/suffixarray_test.go b/src/index/suffixarray/suffixarray_test.go
index 28090de..b6a8112 100644
--- a/src/index/suffixarray/suffixarray_test.go
+++ b/src/index/suffixarray/suffixarray_test.go
@@ -7,9 +7,9 @@
 import (
 	"bytes"
 	"fmt"
+	"io/fs"
 	"io/ioutil"
 	"math/rand"
-	"os"
 	"path/filepath"
 	"regexp"
 	"sort"
@@ -503,7 +503,7 @@
 			return nil, err
 		}
 	case "go":
-		err := filepath.Walk("../..", func(path string, info os.FileInfo, err error) error {
+		err := filepath.Walk("../..", func(path string, info fs.FileInfo, err error) error {
 			if err == nil && strings.HasSuffix(path, ".go") && !info.IsDir() {
 				file, err := ioutil.ReadFile(path)
 				if err != nil {
diff --git a/src/internal/poll/error_test.go b/src/internal/poll/error_test.go
index 06b96f6..abc8b16 100644
--- a/src/internal/poll/error_test.go
+++ b/src/internal/poll/error_test.go
@@ -6,6 +6,7 @@
 
 import (
 	"fmt"
+	"io/fs"
 	"net"
 	"os"
 	"testing"
@@ -37,7 +38,7 @@
 	if nerr, ok := err.(*net.OpError); ok {
 		err = nerr.Err
 	}
-	if nerr, ok := err.(*os.PathError); ok {
+	if nerr, ok := err.(*fs.PathError); ok {
 		err = nerr.Err
 	}
 	if nerr, ok := err.(*os.SyscallError); ok {
diff --git a/src/internal/reflectlite/reflect_mirror_test.go b/src/internal/reflectlite/reflect_mirror_test.go
index fbb6fb3..9b28b13 100644
--- a/src/internal/reflectlite/reflect_mirror_test.go
+++ b/src/internal/reflectlite/reflect_mirror_test.go
@@ -9,6 +9,7 @@
 	"go/ast"
 	"go/parser"
 	"go/token"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -71,7 +72,7 @@
 func loadTypes(path, pkgName string, v visitor) {
 	fset := token.NewFileSet()
 
-	filter := func(fi os.FileInfo) bool {
+	filter := func(fi fs.FileInfo) bool {
 		return strings.HasSuffix(fi.Name(), ".go")
 	}
 	pkgs, err := parser.ParseDir(fset, path, filter, 0)
diff --git a/src/io/ioutil/ioutil.go b/src/io/ioutil/ioutil.go
index acc6ec3..cae41f0 100644
--- a/src/io/ioutil/ioutil.go
+++ b/src/io/ioutil/ioutil.go
@@ -8,6 +8,7 @@
 import (
 	"bytes"
 	"io"
+	"io/fs"
 	"os"
 	"sort"
 	"sync"
@@ -76,7 +77,7 @@
 // WriteFile writes data to a file named by filename.
 // If the file does not exist, WriteFile creates it with permissions perm
 // (before umask); otherwise WriteFile truncates it before writing, without changing permissions.
-func WriteFile(filename string, data []byte, perm os.FileMode) error {
+func WriteFile(filename string, data []byte, perm fs.FileMode) error {
 	f, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, perm)
 	if err != nil {
 		return err
@@ -90,7 +91,7 @@
 
 // ReadDir reads the directory named by dirname and returns
 // a list of directory entries sorted by filename.
-func ReadDir(dirname string) ([]os.FileInfo, error) {
+func ReadDir(dirname string) ([]fs.FileInfo, error) {
 	f, err := os.Open(dirname)
 	if err != nil {
 		return nil, err
diff --git a/src/io/ioutil/tempfile_test.go b/src/io/ioutil/tempfile_test.go
index fcc5101..440c7cf 100644
--- a/src/io/ioutil/tempfile_test.go
+++ b/src/io/ioutil/tempfile_test.go
@@ -5,6 +5,7 @@
 package ioutil_test
 
 import (
+	"io/fs"
 	. "io/ioutil"
 	"os"
 	"path/filepath"
@@ -151,7 +152,7 @@
 
 	badDir := filepath.Join(dir, "not-exist")
 	_, err = TempDir(badDir, "foo")
-	if pe, ok := err.(*os.PathError); !ok || !os.IsNotExist(err) || pe.Path != badDir {
+	if pe, ok := err.(*fs.PathError); !ok || !os.IsNotExist(err) || pe.Path != badDir {
 		t.Errorf("TempDir error = %#v; want PathError for path %q satisifying os.IsNotExist", err, badDir)
 	}
 }
diff --git a/src/net/conf_test.go b/src/net/conf_test.go
index 3c7403e..4c21d56 100644
--- a/src/net/conf_test.go
+++ b/src/net/conf_test.go
@@ -7,7 +7,7 @@
 package net
 
 import (
-	"os"
+	"io/fs"
 	"strings"
 	"testing"
 )
@@ -26,7 +26,7 @@
 	ndots:    1,
 	timeout:  5,
 	attempts: 2,
-	err:      os.ErrNotExist,
+	err:      fs.ErrNotExist,
 }
 
 func TestConfHostLookupOrder(t *testing.T) {
@@ -106,7 +106,7 @@
 			name: "solaris_no_nsswitch",
 			c: &conf{
 				goos:   "solaris",
-				nss:    &nssConf{err: os.ErrNotExist},
+				nss:    &nssConf{err: fs.ErrNotExist},
 				resolv: defaultResolvConf,
 			},
 			hostTests: []nssHostTest{{"google.com", "myhostname", hostLookupCgo}},
@@ -176,7 +176,7 @@
 			name: "linux_no_nsswitch.conf",
 			c: &conf{
 				goos:   "linux",
-				nss:    &nssConf{err: os.ErrNotExist},
+				nss:    &nssConf{err: fs.ErrNotExist},
 				resolv: defaultResolvConf,
 			},
 			hostTests: []nssHostTest{{"google.com", "myhostname", hostLookupDNSFiles}},
diff --git a/src/net/dnsconfig_unix_test.go b/src/net/dnsconfig_unix_test.go
index 4288012..0d7897a 100644
--- a/src/net/dnsconfig_unix_test.go
+++ b/src/net/dnsconfig_unix_test.go
@@ -8,6 +8,7 @@
 
 import (
 	"errors"
+	"io/fs"
 	"os"
 	"reflect"
 	"strings"
@@ -183,7 +184,7 @@
 
 	conf := dnsReadConfig("a-nonexistent-file")
 	if !os.IsNotExist(conf.err) {
-		t.Errorf("missing resolv.conf:\ngot: %v\nwant: %v", conf.err, os.ErrNotExist)
+		t.Errorf("missing resolv.conf:\ngot: %v\nwant: %v", conf.err, fs.ErrNotExist)
 	}
 	conf.err = nil
 	want := &dnsConfig{
diff --git a/src/net/error_test.go b/src/net/error_test.go
index 62dfb9c..7823fdf 100644
--- a/src/net/error_test.go
+++ b/src/net/error_test.go
@@ -12,6 +12,7 @@
 	"fmt"
 	"internal/poll"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"net/internal/socktest"
 	"os"
@@ -97,7 +98,7 @@
 	case *os.SyscallError:
 		nestedErr = err.Err
 		goto third
-	case *os.PathError: // for Plan 9
+	case *fs.PathError: // for Plan 9
 		nestedErr = err.Err
 		goto third
 	}
@@ -531,7 +532,7 @@
 	case *os.SyscallError:
 		nestedErr = err.Err
 		goto third
-	case *os.PathError: // for Plan 9
+	case *fs.PathError: // for Plan 9
 		nestedErr = err.Err
 		goto third
 	}
@@ -546,7 +547,7 @@
 		return nil
 	}
 	switch nestedErr {
-	case os.ErrClosed: // for Plan 9
+	case fs.ErrClosed: // for Plan 9
 		return nil
 	}
 	return fmt.Errorf("unexpected type on 3rd nested level: %T", nestedErr)
@@ -627,7 +628,7 @@
 	case *os.SyscallError:
 		nestedErr = err.Err
 		goto third
-	case *os.PathError: // for Plan 9
+	case *fs.PathError: // for Plan 9
 		nestedErr = err.Err
 		goto third
 	}
@@ -706,7 +707,7 @@
 	case *os.LinkError:
 		nestedErr = err.Err
 		goto third
-	case *os.PathError:
+	case *fs.PathError:
 		nestedErr = err.Err
 		goto third
 	}
@@ -799,7 +800,7 @@
 	switch nestedErr.(type) {
 	case *AddrError, *DNSError:
 		return nil
-	case *os.PathError: // for Plan 9
+	case *fs.PathError: // for Plan 9
 		return nil
 	}
 	return fmt.Errorf("unexpected type on 1st nested level: %T", nestedErr)
diff --git a/src/net/http/example_filesystem_test.go b/src/net/http/example_filesystem_test.go
index e1fd42d..0e81458 100644
--- a/src/net/http/example_filesystem_test.go
+++ b/src/net/http/example_filesystem_test.go
@@ -5,9 +5,9 @@
 package http_test
 
 import (
+	"io/fs"
 	"log"
 	"net/http"
-	"os"
 	"strings"
 )
 
@@ -33,7 +33,7 @@
 
 // Readdir is a wrapper around the Readdir method of the embedded File
 // that filters out all files that start with a period in their name.
-func (f dotFileHidingFile) Readdir(n int) (fis []os.FileInfo, err error) {
+func (f dotFileHidingFile) Readdir(n int) (fis []fs.FileInfo, err error) {
 	files, err := f.File.Readdir(n)
 	for _, file := range files { // Filters out the dot files
 		if !strings.HasPrefix(file.Name(), ".") {
@@ -52,12 +52,12 @@
 // Open is a wrapper around the Open method of the embedded FileSystem
 // that serves a 403 permission error when name has a file or directory
 // with whose name starts with a period in its path.
-func (fs dotFileHidingFileSystem) Open(name string) (http.File, error) {
+func (fsys dotFileHidingFileSystem) Open(name string) (http.File, error) {
 	if containsDotFile(name) { // If dot file, return 403 response
-		return nil, os.ErrPermission
+		return nil, fs.ErrPermission
 	}
 
-	file, err := fs.FileSystem.Open(name)
+	file, err := fsys.FileSystem.Open(name)
 	if err != nil {
 		return nil, err
 	}
@@ -65,7 +65,7 @@
 }
 
 func ExampleFileServer_dotFileHiding() {
-	fs := dotFileHidingFileSystem{http.Dir(".")}
-	http.Handle("/", http.FileServer(fs))
+	fsys := dotFileHidingFileSystem{http.Dir(".")}
+	http.Handle("/", http.FileServer(fsys))
 	log.Fatal(http.ListenAndServe(":8080", nil))
 }
diff --git a/src/net/http/fs.go b/src/net/http/fs.go
index d718fff..0743b5b 100644
--- a/src/net/http/fs.go
+++ b/src/net/http/fs.go
@@ -10,6 +10,7 @@
 	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"mime"
 	"mime/multipart"
 	"net/textproto"
@@ -43,7 +44,7 @@
 
 // mapDirOpenError maps the provided non-nil error from opening name
 // to a possibly better non-nil error. In particular, it turns OS-specific errors
-// about opening files in non-directories into os.ErrNotExist. See Issue 18984.
+// about opening files in non-directories into fs.ErrNotExist. See Issue 18984.
 func mapDirOpenError(originalErr error, name string) error {
 	if os.IsNotExist(originalErr) || os.IsPermission(originalErr) {
 		return originalErr
@@ -59,7 +60,7 @@
 			return originalErr
 		}
 		if !fi.IsDir() {
-			return os.ErrNotExist
+			return fs.ErrNotExist
 		}
 	}
 	return originalErr
@@ -98,8 +99,8 @@
 	io.Closer
 	io.Reader
 	io.Seeker
-	Readdir(count int) ([]os.FileInfo, error)
-	Stat() (os.FileInfo, error)
+	Readdir(count int) ([]fs.FileInfo, error)
+	Stat() (fs.FileInfo, error)
 }
 
 func dirList(w ResponseWriter, r *Request, f File) {
diff --git a/src/net/http/fs_test.go b/src/net/http/fs_test.go
index 4ac73b7..de793b3 100644
--- a/src/net/http/fs_test.go
+++ b/src/net/http/fs_test.go
@@ -10,6 +10,7 @@
 	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"mime"
 	"mime/multipart"
@@ -629,9 +630,9 @@
 func (f *fakeFileInfo) ModTime() time.Time { return f.modtime }
 func (f *fakeFileInfo) IsDir() bool        { return f.dir }
 func (f *fakeFileInfo) Size() int64        { return int64(len(f.contents)) }
-func (f *fakeFileInfo) Mode() os.FileMode {
+func (f *fakeFileInfo) Mode() fs.FileMode {
 	if f.dir {
-		return 0755 | os.ModeDir
+		return 0755 | fs.ModeDir
 	}
 	return 0644
 }
@@ -644,12 +645,12 @@
 }
 
 func (f *fakeFile) Close() error               { return nil }
-func (f *fakeFile) Stat() (os.FileInfo, error) { return f.fi, nil }
-func (f *fakeFile) Readdir(count int) ([]os.FileInfo, error) {
+func (f *fakeFile) Stat() (fs.FileInfo, error) { return f.fi, nil }
+func (f *fakeFile) Readdir(count int) ([]fs.FileInfo, error) {
 	if !f.fi.dir {
-		return nil, os.ErrInvalid
+		return nil, fs.ErrInvalid
 	}
-	var fis []os.FileInfo
+	var fis []fs.FileInfo
 
 	limit := f.entpos + count
 	if count <= 0 || limit > len(f.fi.ents) {
@@ -668,11 +669,11 @@
 
 type fakeFS map[string]*fakeFileInfo
 
-func (fs fakeFS) Open(name string) (File, error) {
+func (fsys fakeFS) Open(name string) (File, error) {
 	name = path.Clean(name)
-	f, ok := fs[name]
+	f, ok := fsys[name]
 	if !ok {
-		return nil, os.ErrNotExist
+		return nil, fs.ErrNotExist
 	}
 	if f.err != nil {
 		return nil, f.err
@@ -747,7 +748,7 @@
 	res.Body.Close()
 }
 
-func mustStat(t *testing.T, fileName string) os.FileInfo {
+func mustStat(t *testing.T, fileName string) fs.FileInfo {
 	fi, err := os.Stat(fileName)
 	if err != nil {
 		t.Fatal(err)
@@ -1081,7 +1082,7 @@
 
 type issue12991File struct{ File }
 
-func (issue12991File) Stat() (os.FileInfo, error) { return nil, os.ErrPermission }
+func (issue12991File) Stat() (fs.FileInfo, error) { return nil, fs.ErrPermission }
 func (issue12991File) Close() error               { return nil }
 
 func TestServeContentErrorMessages(t *testing.T) {
@@ -1091,7 +1092,7 @@
 			err: errors.New("random error"),
 		},
 		"/403": &fakeFileInfo{
-			err: &os.PathError{Err: os.ErrPermission},
+			err: &fs.PathError{Err: fs.ErrPermission},
 		},
 	}
 	ts := httptest.NewServer(FileServer(fs))
@@ -1289,7 +1290,7 @@
 		// Just return back something that's a directory.
 		return Dir(".").Open(".")
 	}
-	return nil, os.ErrNotExist
+	return nil, fs.ErrNotExist
 }
 
 type panicOnSeek struct{ io.ReadSeeker }
diff --git a/src/net/ipsock_plan9.go b/src/net/ipsock_plan9.go
index 2308236..7a4b7a6 100644
--- a/src/net/ipsock_plan9.go
+++ b/src/net/ipsock_plan9.go
@@ -7,6 +7,7 @@
 import (
 	"context"
 	"internal/bytealg"
+	"io/fs"
 	"os"
 	"syscall"
 )
@@ -164,7 +165,7 @@
 	if nonNilInterface(oe.Addr) {
 		oe.Addr = nil
 	}
-	if pe, ok := oe.Err.(*os.PathError); ok {
+	if pe, ok := oe.Err.(*fs.PathError); ok {
 		if _, ok = pe.Err.(syscall.ErrorString); ok {
 			oe.Err = pe.Err
 		}
diff --git a/src/os/error_test.go b/src/os/error_test.go
index 3d92157..060cf59 100644
--- a/src/os/error_test.go
+++ b/src/os/error_test.go
@@ -7,6 +7,7 @@
 import (
 	"errors"
 	"fmt"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -27,7 +28,7 @@
 		t.Fatal("Open should have failed")
 		return
 	}
-	if s := checkErrorPredicate("os.IsExist", os.IsExist, err, os.ErrExist); s != "" {
+	if s := checkErrorPredicate("os.IsExist", os.IsExist, err, fs.ErrExist); s != "" {
 		t.Fatal(s)
 		return
 	}
@@ -39,7 +40,7 @@
 		f.Close()
 		return "Open should have failed"
 	}
-	if s := checkErrorPredicate("os.IsNotExist", os.IsNotExist, err, os.ErrNotExist); s != "" {
+	if s := checkErrorPredicate("os.IsNotExist", os.IsNotExist, err, fs.ErrNotExist); s != "" {
 		return s
 	}
 
@@ -47,7 +48,7 @@
 	if err == nil {
 		return "Chdir should have failed"
 	}
-	if s := checkErrorPredicate("os.IsNotExist", os.IsNotExist, err, os.ErrNotExist); s != "" {
+	if s := checkErrorPredicate("os.IsNotExist", os.IsNotExist, err, fs.ErrNotExist); s != "" {
 		return s
 	}
 	return ""
@@ -91,18 +92,18 @@
 }
 
 var isExistTests = []isExistTest{
-	{&os.PathError{Err: os.ErrInvalid}, false, false},
-	{&os.PathError{Err: os.ErrPermission}, false, false},
-	{&os.PathError{Err: os.ErrExist}, true, false},
-	{&os.PathError{Err: os.ErrNotExist}, false, true},
-	{&os.PathError{Err: os.ErrClosed}, false, false},
-	{&os.LinkError{Err: os.ErrInvalid}, false, false},
-	{&os.LinkError{Err: os.ErrPermission}, false, false},
-	{&os.LinkError{Err: os.ErrExist}, true, false},
-	{&os.LinkError{Err: os.ErrNotExist}, false, true},
-	{&os.LinkError{Err: os.ErrClosed}, false, false},
-	{&os.SyscallError{Err: os.ErrNotExist}, false, true},
-	{&os.SyscallError{Err: os.ErrExist}, true, false},
+	{&fs.PathError{Err: fs.ErrInvalid}, false, false},
+	{&fs.PathError{Err: fs.ErrPermission}, false, false},
+	{&fs.PathError{Err: fs.ErrExist}, true, false},
+	{&fs.PathError{Err: fs.ErrNotExist}, false, true},
+	{&fs.PathError{Err: fs.ErrClosed}, false, false},
+	{&os.LinkError{Err: fs.ErrInvalid}, false, false},
+	{&os.LinkError{Err: fs.ErrPermission}, false, false},
+	{&os.LinkError{Err: fs.ErrExist}, true, false},
+	{&os.LinkError{Err: fs.ErrNotExist}, false, true},
+	{&os.LinkError{Err: fs.ErrClosed}, false, false},
+	{&os.SyscallError{Err: fs.ErrNotExist}, false, true},
+	{&os.SyscallError{Err: fs.ErrExist}, true, false},
 	{nil, false, false},
 }
 
@@ -111,14 +112,14 @@
 		if is := os.IsExist(tt.err); is != tt.is {
 			t.Errorf("os.IsExist(%T %v) = %v, want %v", tt.err, tt.err, is, tt.is)
 		}
-		if is := errors.Is(tt.err, os.ErrExist); is != tt.is {
-			t.Errorf("errors.Is(%T %v, os.ErrExist) = %v, want %v", tt.err, tt.err, is, tt.is)
+		if is := errors.Is(tt.err, fs.ErrExist); is != tt.is {
+			t.Errorf("errors.Is(%T %v, fs.ErrExist) = %v, want %v", tt.err, tt.err, is, tt.is)
 		}
 		if isnot := os.IsNotExist(tt.err); isnot != tt.isnot {
 			t.Errorf("os.IsNotExist(%T %v) = %v, want %v", tt.err, tt.err, isnot, tt.isnot)
 		}
-		if isnot := errors.Is(tt.err, os.ErrNotExist); isnot != tt.isnot {
-			t.Errorf("errors.Is(%T %v, os.ErrNotExist) = %v, want %v", tt.err, tt.err, isnot, tt.isnot)
+		if isnot := errors.Is(tt.err, fs.ErrNotExist); isnot != tt.isnot {
+			t.Errorf("errors.Is(%T %v, fs.ErrNotExist) = %v, want %v", tt.err, tt.err, isnot, tt.isnot)
 		}
 	}
 }
@@ -130,8 +131,8 @@
 
 var isPermissionTests = []isPermissionTest{
 	{nil, false},
-	{&os.PathError{Err: os.ErrPermission}, true},
-	{&os.SyscallError{Err: os.ErrPermission}, true},
+	{&fs.PathError{Err: fs.ErrPermission}, true},
+	{&os.SyscallError{Err: fs.ErrPermission}, true},
 }
 
 func TestIsPermission(t *testing.T) {
@@ -139,8 +140,8 @@
 		if got := os.IsPermission(tt.err); got != tt.want {
 			t.Errorf("os.IsPermission(%#v) = %v; want %v", tt.err, got, tt.want)
 		}
-		if got := errors.Is(tt.err, os.ErrPermission); got != tt.want {
-			t.Errorf("errors.Is(%#v, os.ErrPermission) = %v; want %v", tt.err, got, tt.want)
+		if got := errors.Is(tt.err, fs.ErrPermission); got != tt.want {
+			t.Errorf("errors.Is(%#v, fs.ErrPermission) = %v; want %v", tt.err, got, tt.want)
 		}
 	}
 }
@@ -170,8 +171,8 @@
 }
 
 func TestPathErrorUnwrap(t *testing.T) {
-	pe := &os.PathError{Err: os.ErrInvalid}
-	if !errors.Is(pe, os.ErrInvalid) {
+	pe := &fs.PathError{Err: fs.ErrInvalid}
+	if !errors.Is(pe, fs.ErrInvalid) {
 		t.Error("errors.Is failed, wanted success")
 	}
 }
@@ -181,7 +182,7 @@
 func (e myErrorIs) Is(target error) bool { return target == e.error }
 
 func TestErrorIsMethods(t *testing.T) {
-	if os.IsPermission(myErrorIs{os.ErrPermission}) {
-		t.Error("os.IsPermission(err) = true when err.Is(os.ErrPermission), wanted false")
+	if os.IsPermission(myErrorIs{fs.ErrPermission}) {
+		t.Error("os.IsPermission(err) = true when err.Is(fs.ErrPermission), wanted false")
 	}
 }
diff --git a/src/os/error_unix_test.go b/src/os/error_unix_test.go
index bfc83c9..18bcf3f 100644
--- a/src/os/error_unix_test.go
+++ b/src/os/error_unix_test.go
@@ -7,14 +7,15 @@
 package os_test
 
 import (
+	"io/fs"
 	"os"
 	"syscall"
 )
 
 func init() {
 	isExistTests = append(isExistTests,
-		isExistTest{err: &os.PathError{Err: syscall.EEXIST}, is: true, isnot: false},
-		isExistTest{err: &os.PathError{Err: syscall.ENOTEMPTY}, is: true, isnot: false},
+		isExistTest{err: &fs.PathError{Err: syscall.EEXIST}, is: true, isnot: false},
+		isExistTest{err: &fs.PathError{Err: syscall.ENOTEMPTY}, is: true, isnot: false},
 
 		isExistTest{err: &os.LinkError{Err: syscall.EEXIST}, is: true, isnot: false},
 		isExistTest{err: &os.LinkError{Err: syscall.ENOTEMPTY}, is: true, isnot: false},
@@ -23,9 +24,9 @@
 		isExistTest{err: &os.SyscallError{Err: syscall.ENOTEMPTY}, is: true, isnot: false},
 	)
 	isPermissionTests = append(isPermissionTests,
-		isPermissionTest{err: &os.PathError{Err: syscall.EACCES}, want: true},
-		isPermissionTest{err: &os.PathError{Err: syscall.EPERM}, want: true},
-		isPermissionTest{err: &os.PathError{Err: syscall.EEXIST}, want: false},
+		isPermissionTest{err: &fs.PathError{Err: syscall.EACCES}, want: true},
+		isPermissionTest{err: &fs.PathError{Err: syscall.EPERM}, want: true},
+		isPermissionTest{err: &fs.PathError{Err: syscall.EEXIST}, want: false},
 
 		isPermissionTest{err: &os.LinkError{Err: syscall.EACCES}, want: true},
 		isPermissionTest{err: &os.LinkError{Err: syscall.EPERM}, want: true},
diff --git a/src/os/error_windows_test.go b/src/os/error_windows_test.go
index 1635c10..b8191c5 100644
--- a/src/os/error_windows_test.go
+++ b/src/os/error_windows_test.go
@@ -7,6 +7,7 @@
 package os_test
 
 import (
+	"io/fs"
 	"os"
 	"syscall"
 )
@@ -15,24 +16,24 @@
 	const _ERROR_BAD_NETPATH = syscall.Errno(53)
 
 	isExistTests = append(isExistTests,
-		isExistTest{err: &os.PathError{Err: syscall.ERROR_FILE_NOT_FOUND}, is: false, isnot: true},
+		isExistTest{err: &fs.PathError{Err: syscall.ERROR_FILE_NOT_FOUND}, is: false, isnot: true},
 		isExistTest{err: &os.LinkError{Err: syscall.ERROR_FILE_NOT_FOUND}, is: false, isnot: true},
 		isExistTest{err: &os.SyscallError{Err: syscall.ERROR_FILE_NOT_FOUND}, is: false, isnot: true},
 
-		isExistTest{err: &os.PathError{Err: _ERROR_BAD_NETPATH}, is: false, isnot: true},
+		isExistTest{err: &fs.PathError{Err: _ERROR_BAD_NETPATH}, is: false, isnot: true},
 		isExistTest{err: &os.LinkError{Err: _ERROR_BAD_NETPATH}, is: false, isnot: true},
 		isExistTest{err: &os.SyscallError{Err: _ERROR_BAD_NETPATH}, is: false, isnot: true},
 
-		isExistTest{err: &os.PathError{Err: syscall.ERROR_PATH_NOT_FOUND}, is: false, isnot: true},
+		isExistTest{err: &fs.PathError{Err: syscall.ERROR_PATH_NOT_FOUND}, is: false, isnot: true},
 		isExistTest{err: &os.LinkError{Err: syscall.ERROR_PATH_NOT_FOUND}, is: false, isnot: true},
 		isExistTest{err: &os.SyscallError{Err: syscall.ERROR_PATH_NOT_FOUND}, is: false, isnot: true},
 
-		isExistTest{err: &os.PathError{Err: syscall.ERROR_DIR_NOT_EMPTY}, is: true, isnot: false},
+		isExistTest{err: &fs.PathError{Err: syscall.ERROR_DIR_NOT_EMPTY}, is: true, isnot: false},
 		isExistTest{err: &os.LinkError{Err: syscall.ERROR_DIR_NOT_EMPTY}, is: true, isnot: false},
 		isExistTest{err: &os.SyscallError{Err: syscall.ERROR_DIR_NOT_EMPTY}, is: true, isnot: false},
 	)
 	isPermissionTests = append(isPermissionTests,
-		isPermissionTest{err: &os.PathError{Err: syscall.ERROR_ACCESS_DENIED}, want: true},
+		isPermissionTest{err: &fs.PathError{Err: syscall.ERROR_ACCESS_DENIED}, want: true},
 		isPermissionTest{err: &os.LinkError{Err: syscall.ERROR_ACCESS_DENIED}, want: true},
 		isPermissionTest{err: &os.SyscallError{Err: syscall.ERROR_ACCESS_DENIED}, want: true},
 	)
diff --git a/src/os/example_test.go b/src/os/example_test.go
index 822886f..fbb277b 100644
--- a/src/os/example_test.go
+++ b/src/os/example_test.go
@@ -6,6 +6,7 @@
 
 import (
 	"fmt"
+	"io/fs"
 	"log"
 	"os"
 	"time"
@@ -62,9 +63,9 @@
 		fmt.Println("regular file")
 	case mode.IsDir():
 		fmt.Println("directory")
-	case mode&os.ModeSymlink != 0:
+	case mode&fs.ModeSymlink != 0:
 		fmt.Println("symbolic link")
-	case mode&os.ModeNamedPipe != 0:
+	case mode&fs.ModeNamedPipe != 0:
 		fmt.Println("named pipe")
 	}
 }
diff --git a/src/os/exec/exec_plan9.go b/src/os/exec/exec_plan9.go
index d90bd04..21ac7b7 100644
--- a/src/os/exec/exec_plan9.go
+++ b/src/os/exec/exec_plan9.go
@@ -4,14 +4,14 @@
 
 package exec
 
-import "os"
+import "io/fs"
 
 func init() {
 	skipStdinCopyError = func(err error) bool {
 		// Ignore hungup errors copying to stdin if the program
 		// completed successfully otherwise.
 		// See Issue 35753.
-		pe, ok := err.(*os.PathError)
+		pe, ok := err.(*fs.PathError)
 		return ok &&
 			pe.Op == "write" && pe.Path == "|1" &&
 			pe.Err.Error() == "i/o on hungup channel"
diff --git a/src/os/exec/exec_unix.go b/src/os/exec/exec_unix.go
index 9c3e17d..51c5242 100644
--- a/src/os/exec/exec_unix.go
+++ b/src/os/exec/exec_unix.go
@@ -7,7 +7,7 @@
 package exec
 
 import (
-	"os"
+	"io/fs"
 	"syscall"
 )
 
@@ -16,7 +16,7 @@
 		// Ignore EPIPE errors copying to stdin if the program
 		// completed successfully otherwise.
 		// See Issue 9173.
-		pe, ok := err.(*os.PathError)
+		pe, ok := err.(*fs.PathError)
 		return ok &&
 			pe.Op == "write" && pe.Path == "|1" &&
 			pe.Err == syscall.EPIPE
diff --git a/src/os/exec/exec_windows.go b/src/os/exec/exec_windows.go
index af8cd97..bb937f8 100644
--- a/src/os/exec/exec_windows.go
+++ b/src/os/exec/exec_windows.go
@@ -5,7 +5,7 @@
 package exec
 
 import (
-	"os"
+	"io/fs"
 	"syscall"
 )
 
@@ -15,7 +15,7 @@
 		// to stdin if the program completed successfully otherwise.
 		// See Issue 20445.
 		const _ERROR_NO_DATA = syscall.Errno(0xe8)
-		pe, ok := err.(*os.PathError)
+		pe, ok := err.(*fs.PathError)
 		return ok &&
 			pe.Op == "write" && pe.Path == "|1" &&
 			(pe.Err == syscall.ERROR_BROKEN_PIPE || pe.Err == _ERROR_NO_DATA)
diff --git a/src/os/exec/lp_plan9.go b/src/os/exec/lp_plan9.go
index 5860cbc..e8826a5 100644
--- a/src/os/exec/lp_plan9.go
+++ b/src/os/exec/lp_plan9.go
@@ -6,6 +6,7 @@
 
 import (
 	"errors"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"strings"
@@ -22,7 +23,7 @@
 	if m := d.Mode(); !m.IsDir() && m&0111 != 0 {
 		return nil
 	}
-	return os.ErrPermission
+	return fs.ErrPermission
 }
 
 // LookPath searches for an executable named file in the
diff --git a/src/os/exec/lp_unix.go b/src/os/exec/lp_unix.go
index 93793e0..66c1df7 100644
--- a/src/os/exec/lp_unix.go
+++ b/src/os/exec/lp_unix.go
@@ -8,6 +8,7 @@
 
 import (
 	"errors"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"strings"
@@ -24,7 +25,7 @@
 	if m := d.Mode(); !m.IsDir() && m&0111 != 0 {
 		return nil
 	}
-	return os.ErrPermission
+	return fs.ErrPermission
 }
 
 // LookPath searches for an executable named file in the
diff --git a/src/os/exec/lp_windows.go b/src/os/exec/lp_windows.go
index 9ea3d76..e7a2cdf 100644
--- a/src/os/exec/lp_windows.go
+++ b/src/os/exec/lp_windows.go
@@ -6,6 +6,7 @@
 
 import (
 	"errors"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"strings"
@@ -20,7 +21,7 @@
 		return err
 	}
 	if d.IsDir() {
-		return os.ErrPermission
+		return fs.ErrPermission
 	}
 	return nil
 }
@@ -47,7 +48,7 @@
 			return f, nil
 		}
 	}
-	return "", os.ErrNotExist
+	return "", fs.ErrNotExist
 }
 
 // LookPath searches for an executable named file in the
diff --git a/src/os/os_test.go b/src/os/os_test.go
index c692ba0..8f14263 100644
--- a/src/os/os_test.go
+++ b/src/os/os_test.go
@@ -2526,7 +2526,7 @@
 	if err := file.Close(); err == nil {
 		t.Error("second Close did not fail")
 	} else if pe, ok := err.(*PathError); !ok {
-		t.Errorf("second Close returned unexpected error type %T; expected os.PathError", pe)
+		t.Errorf("second Close returned unexpected error type %T; expected fs.PathError", pe)
 	} else if pe.Err != ErrClosed {
 		t.Errorf("second Close returned %q, wanted %q", err, ErrClosed)
 	} else {
diff --git a/src/os/os_windows_test.go b/src/os/os_windows_test.go
index f03ec75..e002774 100644
--- a/src/os/os_windows_test.go
+++ b/src/os/os_windows_test.go
@@ -12,6 +12,7 @@
 	"internal/syscall/windows/registry"
 	"internal/testenv"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	osexec "os/exec"
@@ -164,11 +165,11 @@
 			t.Errorf("failed to lstat link %v: %v", link, err)
 			continue
 		}
-		if m := fi2.Mode(); m&os.ModeSymlink == 0 {
+		if m := fi2.Mode(); m&fs.ModeSymlink == 0 {
 			t.Errorf("%q should be a link, but is not (mode=0x%x)", link, uint32(m))
 			continue
 		}
-		if m := fi2.Mode(); m&os.ModeDir != 0 {
+		if m := fi2.Mode(); m&fs.ModeDir != 0 {
 			t.Errorf("%q should be a link, not a directory (mode=0x%x)", link, uint32(m))
 			continue
 		}
@@ -681,7 +682,7 @@
 	defer os.Remove("x")
 
 	_, err = os.Stat("x")
-	if _, ok := err.(*os.PathError); !ok {
+	if _, ok := err.(*fs.PathError); !ok {
 		t.Errorf("expected *PathError, got %T: %v\n", err, err)
 	}
 }
@@ -1291,9 +1292,9 @@
 // os.Mkdir(os.DevNull) fails.
 func TestMkdirDevNull(t *testing.T) {
 	err := os.Mkdir(os.DevNull, 777)
-	oserr, ok := err.(*os.PathError)
+	oserr, ok := err.(*fs.PathError)
 	if !ok {
-		t.Fatalf("error (%T) is not *os.PathError", err)
+		t.Fatalf("error (%T) is not *fs.PathError", err)
 	}
 	errno, ok := oserr.Err.(syscall.Errno)
 	if !ok {
diff --git a/src/os/pipe_test.go b/src/os/pipe_test.go
index 429bd81..0593efe 100644
--- a/src/os/pipe_test.go
+++ b/src/os/pipe_test.go
@@ -13,6 +13,7 @@
 	"fmt"
 	"internal/testenv"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	osexec "os/exec"
@@ -46,7 +47,7 @@
 		if err == nil {
 			t.Fatal("unexpected success of Write to broken pipe")
 		}
-		if pe, ok := err.(*os.PathError); ok {
+		if pe, ok := err.(*fs.PathError); ok {
 			err = pe.Err
 		}
 		if se, ok := err.(*os.SyscallError); ok {
@@ -202,10 +203,10 @@
 	}
 	if err == nil {
 		t.Error("I/O on closed pipe unexpectedly succeeded")
-	} else if pe, ok := err.(*os.PathError); !ok {
-		t.Errorf("I/O on closed pipe returned unexpected error type %T; expected os.PathError", pe)
-	} else if pe.Err != os.ErrClosed {
-		t.Errorf("got error %q but expected %q", pe.Err, os.ErrClosed)
+	} else if pe, ok := err.(*fs.PathError); !ok {
+		t.Errorf("I/O on closed pipe returned unexpected error type %T; expected fs.PathError", pe)
+	} else if pe.Err != fs.ErrClosed {
+		t.Errorf("got error %q but expected %q", pe.Err, fs.ErrClosed)
 	} else {
 		t.Logf("I/O returned expected error %q", err)
 	}
@@ -233,7 +234,7 @@
 		defer syscall.SetNonblock(fd, false)
 		_, err := os.Stdin.Read(make([]byte, 1))
 		if err != nil {
-			if perr, ok := err.(*os.PathError); !ok || perr.Err != syscall.EAGAIN {
+			if perr, ok := err.(*fs.PathError); !ok || perr.Err != syscall.EAGAIN {
 				t.Fatalf("read on nonblocking stdin got %q, should have gotten EAGAIN", err)
 			}
 		}
@@ -308,10 +309,10 @@
 		if err == nil {
 			t.Error("I/O on closed pipe unexpectedly succeeded")
 		}
-		if pe, ok := err.(*os.PathError); ok {
+		if pe, ok := err.(*fs.PathError); ok {
 			err = pe.Err
 		}
-		if err != io.EOF && err != os.ErrClosed {
+		if err != io.EOF && err != fs.ErrClosed {
 			t.Errorf("got %v, expected EOF or closed", err)
 		}
 	}(c2)
diff --git a/src/os/removeall_test.go b/src/os/removeall_test.go
index 1e5c650..bc9c468 100644
--- a/src/os/removeall_test.go
+++ b/src/os/removeall_test.go
@@ -359,7 +359,7 @@
 			t.Errorf("got %q, expected pathErr.path %q", g, w)
 		}
 	} else {
-		t.Errorf("got %T, expected *os.PathError", err)
+		t.Errorf("got %T, expected *fs.PathError", err)
 	}
 
 	for _, dir := range dirs {
diff --git a/src/os/signal/signal_cgo_test.go b/src/os/signal/signal_cgo_test.go
index a117221..a8a4856 100644
--- a/src/os/signal/signal_cgo_test.go
+++ b/src/os/signal/signal_cgo_test.go
@@ -17,6 +17,7 @@
 	"context"
 	"fmt"
 	"io"
+	"io/fs"
 	"os"
 	"os/exec"
 	ptypkg "os/signal/internal/pty"
@@ -127,7 +128,7 @@
 				if len(line) > 0 || len(handled) > 0 {
 					t.Logf("%q", append(handled, line...))
 				}
-				if perr, ok := err.(*os.PathError); ok {
+				if perr, ok := err.(*fs.PathError); ok {
 					err = perr.Err
 				}
 				// EOF means pty is closed.
diff --git a/src/os/stat_test.go b/src/os/stat_test.go
index 60f3b4c..88b7890 100644
--- a/src/os/stat_test.go
+++ b/src/os/stat_test.go
@@ -6,6 +6,7 @@
 
 import (
 	"internal/testenv"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -14,7 +15,7 @@
 )
 
 // testStatAndLstat verifies that all os.Stat, os.Lstat os.File.Stat and os.Readdir work.
-func testStatAndLstat(t *testing.T, path string, isLink bool, statCheck, lstatCheck func(*testing.T, string, os.FileInfo)) {
+func testStatAndLstat(t *testing.T, path string, isLink bool, statCheck, lstatCheck func(*testing.T, string, fs.FileInfo)) {
 	// test os.Stat
 	sfi, err := os.Stat(path)
 	if err != nil {
@@ -70,7 +71,7 @@
 		}
 	}
 
-	// test os.FileInfo returned by os.Readdir
+	// test fs.FileInfo returned by os.Readdir
 	if len(path) > 0 && os.IsPathSeparator(path[len(path)-1]) {
 		// skip os.Readdir test of directories with slash at the end
 		return
@@ -88,7 +89,7 @@
 		t.Error(err)
 		return
 	}
-	var lsfi2 os.FileInfo
+	var lsfi2 fs.FileInfo
 	base := filepath.Base(path)
 	for _, fi2 := range fis {
 		if fi2.Name() == base {
@@ -108,34 +109,34 @@
 }
 
 // testIsDir verifies that fi refers to directory.
-func testIsDir(t *testing.T, path string, fi os.FileInfo) {
+func testIsDir(t *testing.T, path string, fi fs.FileInfo) {
 	t.Helper()
 	if !fi.IsDir() {
 		t.Errorf("%q should be a directory", path)
 	}
-	if fi.Mode()&os.ModeSymlink != 0 {
+	if fi.Mode()&fs.ModeSymlink != 0 {
 		t.Errorf("%q should not be a symlink", path)
 	}
 }
 
 // testIsSymlink verifies that fi refers to symlink.
-func testIsSymlink(t *testing.T, path string, fi os.FileInfo) {
+func testIsSymlink(t *testing.T, path string, fi fs.FileInfo) {
 	t.Helper()
 	if fi.IsDir() {
 		t.Errorf("%q should not be a directory", path)
 	}
-	if fi.Mode()&os.ModeSymlink == 0 {
+	if fi.Mode()&fs.ModeSymlink == 0 {
 		t.Errorf("%q should be a symlink", path)
 	}
 }
 
 // testIsFile verifies that fi refers to file.
-func testIsFile(t *testing.T, path string, fi os.FileInfo) {
+func testIsFile(t *testing.T, path string, fi fs.FileInfo) {
 	t.Helper()
 	if fi.IsDir() {
 		t.Errorf("%q should not be a directory", path)
 	}
-	if fi.Mode()&os.ModeSymlink != 0 {
+	if fi.Mode()&fs.ModeSymlink != 0 {
 		t.Errorf("%q should not be a symlink", path)
 	}
 }
diff --git a/src/path/filepath/example_unix_walk_test.go b/src/path/filepath/example_unix_walk_test.go
index fa8b8e3..66dc7f6 100644
--- a/src/path/filepath/example_unix_walk_test.go
+++ b/src/path/filepath/example_unix_walk_test.go
@@ -8,6 +8,7 @@
 
 import (
 	"fmt"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -40,7 +41,7 @@
 	subDirToSkip := "skip"
 
 	fmt.Println("On Unix:")
-	err = filepath.Walk(".", func(path string, info os.FileInfo, err error) error {
+	err = filepath.Walk(".", func(path string, info fs.FileInfo, err error) error {
 		if err != nil {
 			fmt.Printf("prevent panic by handling failure accessing a path %q: %v\n", path, err)
 			return err
diff --git a/src/path/filepath/path.go b/src/path/filepath/path.go
index 26f1833..dffd27d 100644
--- a/src/path/filepath/path.go
+++ b/src/path/filepath/path.go
@@ -13,6 +13,7 @@
 
 import (
 	"errors"
+	"io/fs"
 	"os"
 	"sort"
 	"strings"
@@ -339,7 +340,7 @@
 // visited by Walk. The path argument contains the argument to Walk as a
 // prefix; that is, if Walk is called with "dir", which is a directory
 // containing the file "a", the walk function will be called with argument
-// "dir/a". The info argument is the os.FileInfo for the named path.
+// "dir/a". The info argument is the fs.FileInfo for the named path.
 //
 // If there was a problem walking to the file or directory named by path, the
 // incoming error will describe the problem and the function can decide how
@@ -350,12 +351,12 @@
 // Walk skips the directory's contents entirely. If the function returns SkipDir
 // when invoked on a non-directory file, Walk skips the remaining files in the
 // containing directory.
-type WalkFunc func(path string, info os.FileInfo, err error) error
+type WalkFunc func(path string, info fs.FileInfo, err error) error
 
 var lstat = os.Lstat // for testing
 
 // walk recursively descends path, calling walkFn.
-func walk(path string, info os.FileInfo, walkFn WalkFunc) error {
+func walk(path string, info fs.FileInfo, walkFn WalkFunc) error {
 	if !info.IsDir() {
 		return walkFn(path, info, nil)
 	}
diff --git a/src/path/filepath/path_test.go b/src/path/filepath/path_test.go
index 6a8700e..7dc8b60 100644
--- a/src/path/filepath/path_test.go
+++ b/src/path/filepath/path_test.go
@@ -8,6 +8,7 @@
 	"errors"
 	"fmt"
 	"internal/testenv"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -393,7 +394,7 @@
 // Assumes that each node name is unique. Good enough for a test.
 // If clear is true, any incoming error is cleared before return. The errors
 // are always accumulated, though.
-func mark(info os.FileInfo, err error, errors *[]error, clear bool) error {
+func mark(info fs.FileInfo, err error, errors *[]error, clear bool) error {
 	name := info.Name()
 	walkTree(tree, tree.name, func(path string, n *Node) {
 		if n.name == name {
@@ -454,7 +455,7 @@
 	makeTree(t)
 	errors := make([]error, 0, 10)
 	clear := true
-	markFn := func(path string, info os.FileInfo, err error) error {
+	markFn := func(path string, info fs.FileInfo, err error) error {
 		return mark(info, err, &errors, clear)
 	}
 	// Expect no errors.
@@ -543,7 +544,7 @@
 	touch(t, filepath.Join(td, "dir/foo2"))
 
 	sawFoo2 := false
-	walker := func(path string, info os.FileInfo, err error) error {
+	walker := func(path string, info fs.FileInfo, err error) error {
 		if strings.HasSuffix(path, "foo2") {
 			sawFoo2 = true
 		}
@@ -589,14 +590,14 @@
 		*filepath.LstatP = os.Lstat
 	}()
 	statErr := errors.New("some stat error")
-	*filepath.LstatP = func(path string) (os.FileInfo, error) {
+	*filepath.LstatP = func(path string) (fs.FileInfo, error) {
 		if strings.HasSuffix(path, "stat-error") {
 			return nil, statErr
 		}
 		return os.Lstat(path)
 	}
 	got := map[string]error{}
-	err = filepath.Walk(td, func(path string, fi os.FileInfo, err error) error {
+	err = filepath.Walk(td, func(path string, fi fs.FileInfo, err error) error {
 		rel, _ := filepath.Rel(td, path)
 		got[filepath.ToSlash(rel)] = err
 		return nil
@@ -1289,7 +1290,7 @@
 	ken := filepath.Join(root, "ken")
 	seenBugs := false
 	seenKen := false
-	err = filepath.Walk(root, func(pth string, info os.FileInfo, err error) error {
+	err = filepath.Walk(root, func(pth string, info fs.FileInfo, err error) error {
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -1338,7 +1339,7 @@
 	}
 
 	var visited []string
-	err = filepath.Walk(tmpdir, func(path string, info os.FileInfo, err error) error {
+	err = filepath.Walk(tmpdir, func(path string, info fs.FileInfo, err error) error {
 		if err != nil {
 			t.Fatal(err)
 		}
diff --git a/src/path/filepath/path_windows_test.go b/src/path/filepath/path_windows_test.go
index f7c454b..990f186 100644
--- a/src/path/filepath/path_windows_test.go
+++ b/src/path/filepath/path_windows_test.go
@@ -8,6 +8,7 @@
 	"flag"
 	"fmt"
 	"internal/testenv"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -34,7 +35,7 @@
 
 	const (
 		cmdfile             = `printdir.cmd`
-		perm    os.FileMode = 0700
+		perm    fs.FileMode = 0700
 	)
 
 	tmp, err := ioutil.TempDir("", "testWinSplitListTestIsValid")
diff --git a/src/path/filepath/symlink.go b/src/path/filepath/symlink.go
index 335b315..6fefd159 100644
--- a/src/path/filepath/symlink.go
+++ b/src/path/filepath/symlink.go
@@ -6,6 +6,7 @@
 
 import (
 	"errors"
+	"io/fs"
 	"os"
 	"runtime"
 	"syscall"
@@ -85,7 +86,7 @@
 			return "", err
 		}
 
-		if fi.Mode()&os.ModeSymlink == 0 {
+		if fi.Mode()&fs.ModeSymlink == 0 {
 			if !fi.Mode().IsDir() && end < len(path) {
 				return "", syscall.ENOTDIR
 			}
diff --git a/src/runtime/testdata/testprogcgo/exec.go b/src/runtime/testdata/testprogcgo/exec.go
index 94da5dc..15723c7 100644
--- a/src/runtime/testdata/testprogcgo/exec.go
+++ b/src/runtime/testdata/testprogcgo/exec.go
@@ -31,6 +31,7 @@
 
 import (
 	"fmt"
+	"io/fs"
 	"os"
 	"os/exec"
 	"os/signal"
@@ -98,7 +99,7 @@
 
 // isEAGAIN reports whether err is an EAGAIN error from a process execution.
 func isEAGAIN(err error) bool {
-	if p, ok := err.(*os.PathError); ok {
+	if p, ok := err.(*fs.PathError); ok {
 		err = p.Err
 	}
 	return err == syscall.EAGAIN
diff --git a/src/syscall/syscall_js.go b/src/syscall/syscall_js.go
index dfb4a27..0ab8c3f 100644
--- a/src/syscall/syscall_js.go
+++ b/src/syscall/syscall_js.go
@@ -49,7 +49,7 @@
 // using errors.Is. For example:
 //
 //	_, _, err := syscall.Syscall(...)
-//	if errors.Is(err, os.ErrNotExist) ...
+//	if errors.Is(err, fs.ErrNotExist) ...
 type Errno uintptr
 
 func (e Errno) Error() string {
diff --git a/src/syscall/syscall_linux_test.go b/src/syscall/syscall_linux_test.go
index c5008f2..93a4d236 100644
--- a/src/syscall/syscall_linux_test.go
+++ b/src/syscall/syscall_linux_test.go
@@ -8,6 +8,7 @@
 	"bufio"
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -353,7 +354,7 @@
 		t.Fatalf("failed to chown test binary %q, %v", tmpBinary, err)
 	}
 
-	err = os.Chmod(tmpBinary, 0755|os.ModeSetuid)
+	err = os.Chmod(tmpBinary, 0755|fs.ModeSetuid)
 	if err != nil {
 		t.Fatalf("failed to set setuid bit on test binary %q, %v", tmpBinary, err)
 	}
diff --git a/src/syscall/syscall_plan9.go b/src/syscall/syscall_plan9.go
index 1648e40..d16cad4 100644
--- a/src/syscall/syscall_plan9.go
+++ b/src/syscall/syscall_plan9.go
@@ -25,7 +25,7 @@
 // using errors.Is. For example:
 //
 //	_, _, err := syscall.Syscall(...)
-//	if errors.Is(err, os.ErrNotExist) ...
+//	if errors.Is(err, fs.ErrNotExist) ...
 type ErrorString string
 
 func (e ErrorString) Error() string { return string(e) }
diff --git a/src/syscall/syscall_unix.go b/src/syscall/syscall_unix.go
index 91c939e..786ad34 100644
--- a/src/syscall/syscall_unix.go
+++ b/src/syscall/syscall_unix.go
@@ -110,7 +110,7 @@
 // using errors.Is. For example:
 //
 //	_, _, err := syscall.Syscall(...)
-//	if errors.Is(err, os.ErrNotExist) ...
+//	if errors.Is(err, fs.ErrNotExist) ...
 type Errno uintptr
 
 func (e Errno) Error() string {
diff --git a/src/syscall/syscall_windows.go b/src/syscall/syscall_windows.go
index f62c00d..40c43de 100644
--- a/src/syscall/syscall_windows.go
+++ b/src/syscall/syscall_windows.go
@@ -106,7 +106,7 @@
 // using errors.Is. For example:
 //
 //	_, _, err := syscall.Syscall(...)
-//	if errors.Is(err, os.ErrNotExist) ...
+//	if errors.Is(err, fs.ErrNotExist) ...
 type Errno uintptr
 
 func langid(pri, sub uint16) uint32 { return uint32(sub)<<10 | uint32(pri) }