code: func encodeToken(token *oauth2.Token) string {
  	if token == nil {
  		return ""
  	}
  	var seconds int64
  	if !token.Expiry.IsZero() {
  		seconds = token.Expiry.Unix()
  	}
  	return token.AccessToken + " " + token.RefreshToken + " " + strconv.FormatInt(seconds, 10)
  }
docs: // encodeToken encodes the oauth2.Token as
  // AccessToken + " " + RefreshToken + " " + Expiry.Unix()