protected function sendAsyncInternal(RequestInterface $request, callable $success, callable $error, int $retryCount = 0)
    {
        if (!$this->curlMultiHandle) {
            $this->curlMultiHandle = curl_multi_init();
        }
        $curl = curl_init();
        curl_setopt_array(
            $curl,
            $this->createCurlSettingsArray($request)
        );
        curl_multi_add_handle($this->curlMultiHandle, $curl);

        $resourceId = (int) $curl;
        $this->headerLinesMap[$resourceId] = [];
        $this->curlMultiMap[$resourceId] = [
            $request,
            $success,
            $error,
            $retryCount,
        ];
    }