code: func (oauth *Oauth) Redirect(writer http.ResponseWriter, req *http.Request, redirectURI, scope, state string) error {
  	location, err := oauth.GetRedirectURL(redirectURI, scope, state)
  	if err != nil {
  		return err
  	}
  	http.Redirect(writer, req, location, 302)
  	return nil
  }
docs: //Redirect 跳转到网页授权