code: func SignStr(value, secret string, expires time.Time) string {
  	return authcookie.New(value, expires, []byte(secret))
  }
docs: // SignStr signs and timestamps a string so it cannot be forged.
  // 
  // Normally used via Sign, but provided as a separate method for
  // non-cookie uses. To decode a value not stored as a cookie use the
  // DecodeStr function.