[code]
func md5_file(filename string) (string, error) {
	f, err := os.Open(filename)
	if err != nil {
		return "", err
	}
	defer f.Close()
	h := md5.New()
	if _, err := io.Copy(h, f); err != nil {
		return "", err
	}
	fmt.Sprintf("%x", h.Sum(nil))
}
[/code]