code: func (d *Doer) Post(url string, body io.Reader, bodyType string, response interface{}) (*http.Response, error) {
  	req, err := d.newRequest(http.MethodPost, url, body, contentType(bodyType))
  	if err != nil {
  		return nil, err
  	}
  
  	return d.do(req, response)
  }
docs: // Post performs a POST request with a proper User-Agent string.
  // If "response" is not provided, callers should close resp.Body when done reading from it.