code: func (r Redirect) Render(w http.ResponseWriter) error {
  	// todo(thinkerou): go1.6 not support StatusPermanentRedirect(308)
  	// when we upgrade go version we can use http.StatusPermanentRedirect
  	if (r.Code < 300 || r.Code > 308) && r.Code != 201 {
  		panic(fmt.Sprintf("Cannot redirect with status code %d", r.Code))
  	}
  	http.Redirect(w, r.Request, r.Location, r.Code)
  	return nil
  }
docs: // Render (Redirect) redirects the http request to new location and writes redirect response.