code: func (s *Service) FormRedirect(r *http.Request, host string) string {
  	rq := r.URL.RawQuery
  	if rq != "" {
  		rq = fmt.Sprintf("?%s", rq)
  	}
  	return fmt.Sprintf("%s://%s%s%s", s.protocol(), host, r.URL.Path, rq)
  }
docs: // FormRedirect returns the value for the "Location" header for a 301 response.