code: func HasBody() ResponseCondition {
  	return func(res *http.Response) error {
  		body, err := ioutil.ReadAll(res.Body)
  		if err != nil {
  			return fmt.Errorf("failed to read response body: %s", err)
  		}
  
  		if len(body) == 0 {
  			return errors.New("response doesn't have body content")
  		}
  		return nil
  	}
  }
docs: // HasBody returns a retry condition function.
  // The condition returns an error if the request body does not have body content.