src/Request.php
public function setHttpVersion($httpVersion)
    {
        if (in_array($httpVersion, [
                CURL_HTTP_VERSION_NONE,
                CURL_HTTP_VERSION_1_0,
                CURL_HTTP_VERSION_1_1,
                CURL_HTTP_VERSION_2,
            ]
        )) {
            $this->curlOptions[ CURLOPT_HTTP_VERSION ] = $httpVersion;
        }

        return $this;
    }
public function setHttpVersion($httpVersion)
    {
        if (in_array($httpVersion, [
                CURL_HTTP_VERSION_NONE,
                CURL_HTTP_VERSION_1_0,
                CURL_HTTP_VERSION_1_1,
                CURL_HTTP_VERSION_2,
            ]
        )) {
            $this->curlOptions[ CURLOPT_HTTP_VERSION ] = $httpVersion;
        }

        return $this;
    }
Request::setHttpVersion

Sets which http version to use (default, lets CURL decide which version to use).

@param int $httpVersion Supported encodings are "CURL_HTTP_VERSION_NONE", "CURL_HTTP_VERSION_1_0",
"CURL_HTTP_VERSION_1_1", and "CURL_HTTP_VERSION_2".

@return static