diff --git a/src/cmd/go/internal/toolchain/select.go b/src/cmd/go/internal/toolchain/select.go
index c27bcb5bbdd..192fb62fc26 100644
--- a/src/cmd/go/internal/toolchain/select.go
+++ b/src/cmd/go/internal/toolchain/select.go
@@ -25,7 +25,6 @@ import (
 	"cmd/go/internal/base"
 	"cmd/go/internal/cfg"
 	"cmd/go/internal/gover"
-	"cmd/go/internal/modfetch"
 	"cmd/go/internal/modload"
 	"cmd/go/internal/run"
 	"cmd/go/internal/work"
@@ -86,8 +85,10 @@ func FilterEnv(env []string) []string {
 	return out
 }
 
-var counterErrorsInvalidToolchainInFile = counter.New("go/errors:invalid-toolchain-in-file")
-var toolchainTrace = godebug.New("#toolchaintrace").Value() == "1"
+var (
+	counterErrorsInvalidToolchainInFile = counter.New("go/errors:invalid-toolchain-in-file")
+	toolchainTrace                      = godebug.New("#toolchaintrace").Value() == "1"
+)
 
 // Select invokes a different Go toolchain if directed by
 // the GOTOOLCHAIN environment variable or the user's configuration
@@ -360,7 +361,7 @@ func Exec(s *modload.State, gotoolchain string) {
 		Path:    gotoolchainModule,
 		Version: gotoolchainVersion + "-" + gotoolchain + "." + runtime.GOOS + "-" + runtime.GOARCH,
 	}
-	dir, err := modfetch.Fetcher_.Download(context.Background(), m)
+	dir, err := s.Fetcher().Download(context.Background(), m)
 	if err != nil {
 		if errors.Is(err, fs.ErrNotExist) {
 			toolVers := gover.FromToolchain(gotoolchain)
@@ -380,7 +381,7 @@ func Exec(s *modload.State, gotoolchain string) {
 		if err != nil {
 			base.Fatalf("download %s: %v", gotoolchain, err)
 		}
-		if info.Mode()&0111 == 0 {
+		if info.Mode()&0o111 == 0 {
 			// allowExec sets the exec permission bits on all files found in dir if pattern is the empty string,
 			// or only those files that match the pattern if it's non-empty.
 			allowExec := func(dir, pattern string) {
@@ -399,7 +400,7 @@ func Exec(s *modload.State, gotoolchain string) {
 						if err != nil {
 							return err
 						}
-						if err := os.Chmod(path, info.Mode()&0777|0111); err != nil {
+						if err := os.Chmod(path, info.Mode()&0o777|0o111); err != nil {
 							return err
 						}
 					}
diff --git a/src/cmd/go/internal/toolchain/switch.go b/src/cmd/go/internal/toolchain/switch.go
index 4ddc28a0e90..ff4fce03074 100644
--- a/src/cmd/go/internal/toolchain/switch.go
+++ b/src/cmd/go/internal/toolchain/switch.go
@@ -97,7 +97,7 @@ func (s *Switcher) Switch(ctx context.Context) {
 	}
 
 	// Switch to newer Go toolchain if necessary and possible.
-	tv, err := NewerToolchain(ctx, s.TooNew.GoVersion)
+	tv, err := NewerToolchain(ctx, s.loaderstate.Fetcher(), s.TooNew.GoVersion)
 	if err != nil {
 		for _, err := range s.Errors {
 			base.Error(err)
@@ -130,8 +130,11 @@ func SwitchOrFatal(loaderstate *modload.State, ctx context.Context, err error) {
 // If the latest major release is 1.N.0, we use the latest patch release of 1.(N-1) if that's >= version.
 // Otherwise we use the latest 1.N if that's allowed.
 // Otherwise we use the latest release.
-func NewerToolchain(ctx context.Context, version string) (string, error) {
-	fetch := autoToolchains
+func NewerToolchain(ctx context.Context, f *modfetch.Fetcher, version string) (string, error) {
+	fetch := func(ctx context.Context) ([]string, error) {
+		return autoToolchains(ctx, f)
+	}
+
 	if !HasAuto() {
 		fetch = pathToolchains
 	}
@@ -143,10 +146,10 @@ func NewerToolchain(ctx context.Context, version string) (string, error) {
 }
 
 // autoToolchains returns the list of toolchain versions available to GOTOOLCHAIN=auto or =min+auto mode.
-func autoToolchains(ctx context.Context) ([]string, error) {
+func autoToolchains(ctx context.Context, f *modfetch.Fetcher) ([]string, error) {
 	var versions *modfetch.Versions
 	err := modfetch.TryProxies(func(proxy string) error {
-		v, err := modfetch.Fetcher_.Lookup(ctx, proxy, "go").Versions(ctx, "")
+		v, err := f.Lookup(ctx, proxy, "go").Versions(ctx, "")
 		if err != nil {
 			return err
 		}