code: func (a *Authenticator) Client() (*http.Client, error) {
  	transport, err := a.Transport()
  	if err != nil {
  		return nil, err
  	}
  	return &http.Client{Transport: transport}, nil
  }
docs: // Client optionally performs a login and returns http.Client.
  //
  // It uses transport returned by Transport(). See documentation for LoginMode
  // for more details.