code: func Post(url string, r io.Reader) error {
  	status, _, rc, err := DefaultClient.Post(url, nil, r)
  	if err != nil {
  		return err
  	}
  	defer rc.Close()
  	if !status.IsSuccess() {
  		return &StatusError{status}
  	}
  	return nil
  }
docs: // Post issues a POST request using the DefaultClient using r as the body.
  // If the status code was not a success code, it will be returned as an error.