code: func base64URLDecode(s string) (string, error) {
  	v, err := base64.URLEncoding.DecodeString(s)
  	if err != nil {
  		return "", errors.Wrap(err, "base64URLDecode")
  	}
  	return string(v), nil
  }
docs: // base64URLDecode decodes the given string as a URL-safe base64 string.