"bytes"
	"strings"
)

var nl = []byte("\n")

// GoModLookup takes go.mod or go.work content,
// finds the first line in the file starting with the given key,
// and returns the value associated with that key.
//
// Lookup should only be used with non-factored verbs
// such as "go" and "toolchain", usually to find versions
// or version-like strings.
func GoModLookup(gomod []byte, key string) string {
	for len(gomod) > 0 {

		file = modload.FindGoMod(wd)
	}
	if file == "" {
		return "", "", ""
	}

	data, err := os.ReadFile(file)
	if err != nil {
		base.Fatalf("%v", err)
	}
	return file, gover.GoModLookup(data, "go"), gover.GoModLookup(data, "toolchain")
}

// goInstallVersion reports whether the command line is go install m@v or go run m@v.
// If so, Select must not read the go.mod or go.work file in "auto" or "path" mode.

			return "", err
		}
		checkMod(ctx, mod)

		// If go.mod exists (not an old legacy module), check version is not too new.
		if data, err := os.ReadFile(filepath.Join(dir, "go.mod")); err == nil {
			goVersion := gover.GoModLookup(data, "go")
			if gover.Compare(goVersion, gover.Local()) > 0 {
				return "", &gover.TooNewError{What: mod.String(), GoVersion: goVersion}
			}
		} else if !errors.Is(err, fs.ErrNotExist) {
			return "", err
		}

	if err != nil {
		return err
	}

	if gomod, err := r.code.ReadFile(ctx, rev, filepath.Join(subdir, "go.mod"), codehost.MaxGoMod); err == nil {
		goVers := gover.GoModLookup(gomod, "go")
		if gover.Compare(goVers, gover.Local()) > 0 {
			return &gover.TooNewError{What: r.ModulePath() + "@" + version, GoVersion: goVers}
		}
	} else if !errors.Is(err, fs.ErrNotExist) {
		return err