code: func (t *traceTransport) RoundTrip(req *http.Request) (*http.Response, error) {
  	if dump, err := httputil.DumpRequest(req, true); err == nil {
  		t.logger.Printf("%s", dump)
  	}
  
  	resp, err := t.transport.RoundTrip(req)
  	if err != nil {
  		return nil, err
  	}
  
  	if dump, err := httputil.DumpResponse(resp, true); err == nil {
  		t.logger.Printf("%s", dump)
  	}
  
  	return resp, nil
  }
docs: // RoundTrip executes a single HTTP transaction