}

// autoToolchains returns the list of toolchain versions available to GOTOOLCHAIN=auto or =min+auto mode.
func autoToolchains(ctx context.Context) ([]string, error) {
	var versions *modfetch.Versions
	err := modfetch.TryProxies(func(proxy string) error {
		v, err := modfetch.Lookup(ctx, proxy, "go").Versions(ctx, "")
		if err != nil {
			return err
		}
		versions = v
		return nil
	})
	if err != nil {
		return nil, err

	}

	if file, info, err := readDiskStat(ctx, path, version); err == nil {
		return info, file, nil
	}

	var info *RevInfo
	var err2info map[error]*RevInfo
	err := TryProxies(func(proxy string) error {
		i, err := Lookup(ctx, proxy, path).Stat(ctx, version)
		if err == nil {
			info = i
		} else {
			if err2info == nil {
				err2info = make(map[error]*RevInfo)
			}

	if err != nil {
		return err
	}
	defer func() {
		if err != nil {
			f.Close()
			os.Remove(f.Name())
		}
	}()

	var unrecoverableErr error
	err = TryProxies(func(proxy string) error {
		if unrecoverableErr != nil {
			return unrecoverableErr
		}
		repo := Lookup(ctx, proxy, mod.Path)
		err := repo.Zip(ctx, f, mod.Version)
		if err != nil {