private function curlOptions()
    {
        $options = [
            // CURLOPT_VERBOSE => true,
            CURLOPT_CONNECTTIMEOUT => $this->connectionTimeout,
            CURLOPT_HEADER => true,
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_SSL_VERIFYHOST => 2,
            CURLOPT_SSL_VERIFYPEER => true,
            CURLOPT_TIMEOUT => $this->timeout,
            CURLOPT_USERAGENT => $this->userAgent,
        ];

        if ($this->useCAFile()) {
            $options[CURLOPT_CAINFO] = __DIR__ . DIRECTORY_SEPARATOR . 'cacert.pem';
        }

        if ($this->gzipEncoding) {
            $options[CURLOPT_ENCODING] = 'gzip';
        }

        if (!empty($this->proxy)) {
            $options[CURLOPT_PROXY] = $this->proxy['CURLOPT_PROXY'];
            $options[CURLOPT_PROXYUSERPWD] = $this->proxy['CURLOPT_PROXYUSERPWD'];
            $options[CURLOPT_PROXYPORT] = $this->proxy['CURLOPT_PROXYPORT'];
            $options[CURLOPT_PROXYAUTH] = CURLAUTH_BASIC;
            $options[CURLOPT_PROXYTYPE] = CURLPROXY_HTTP;
        }

        return $options;
    }