code: public function post($url, $params = [])
      {
          $key = is_array($params) ? 'form_params' : 'body';
  
          return $this->request('POST', $url, [$key => $params]);
      }
docs: Send A Http POST Request
  
  @param  string $url
  @param  array  $params
  
  @return \Psr\Http\Message\ResponseInterface