code: func (t *CookieAuthTransport) buildAuthRequest() (*http.Request, error) {
  	body := struct {
  		Username string `json:"username"`
  		Password string `json:"password"`
  	}{
  		t.Username,
  		t.Password,
  	}
  
  	b := new(bytes.Buffer)
  	json.NewEncoder(b).Encode(body)
  
  	req, err := http.NewRequest("POST", t.AuthURL, b)
  	if err != nil {
  		return nil, err
  	}
  
  	req.Header.Set("Content-Type", "application/json")
  	return req, nil
  }
docs: // getAuthRequest assembles the request to get the authenticated cookie