code: func (rt *upgradeRequestRoundTripper) WrapRequest(req *http.Request) (*http.Request, error) {
  	resp, err := rt.upgrader.RoundTrip(req)
  	if err != nil {
  		return nil, err
  	}
  	return resp.Request, nil
  }
docs: // WriteToRequest calls the nested upgrader and then copies the returned request
  // fields onto the passed request.