code: func requireOK(d time.Duration, resp *http.Response, e error) (time.Duration, *http.Response, error) {
  	if e != nil {
  		if resp != nil {
  			resp.Body.Close()
  		}
  		return d, nil, e
  	}
  	if resp.StatusCode != 200 {
  		return d, nil, generateUnexpectedResponseCodeError(resp)
  	}
  	return d, resp, nil
  }
docs: // requireOK is used to wrap doRequest and check for a 200