code: func TokenExpiresIn(ctx context.Context, t *Token, lifetime time.Duration) bool {
  	if t == nil || t.AccessToken == "" {
  		return true
  	}
  	if t.Expiry.IsZero() {
  		return false
  	}
  	return t.Expiry.Round(0).Before(clock.Now(ctx).Add(lifetime))
  }
docs: // TokenExpiresIn returns True if the token is not valid or expires within given
  // duration.
  //
  // The function returns True in any of the following conditions:
  //  * The token is not valid.
  //  * The token expires before now+lifetime.
  //
  // In all other cases it returns False.