code: func (s *Server) URL() (u *url.URL, err error) {
  	if s.Scheme == "" {
  		return u, fmt.Errorf("Server %s:%d has no scheme, cannot make a URL", s.Host, s.Port)
  	}
  
  	ustring := fmt.Sprintf("%s://%s:%d", s.Scheme, s.Host, s.Port)
  
  	u, err = url.Parse(ustring)
  	if err != nil {
  		return u, fmt.Errorf("Could not parse %s: %s", ustring, err)
  	}
  
  	return
  }
docs: // URL creates a correct url from the server if scheme is known