code: func (s *SecureCookie) timestamp() int64 {
  	if s.timeFunc == nil {
  		return time.Now().UTC().Unix()
  	}
  	return s.timeFunc()
  }
docs: // timestamp returns the current timestamp, in seconds.
  //
  // For testing purposes, the function that generates the timestamp can be
  // overridden. If not set, it will return time.Now().UTC().Unix().