pub async fn connect(
    connection: Connection,
    method: &str,
    file_name: &str,
    file_path: &str,
    path: &str,
    query: Option<&str>,
    address: &SocketAddr,
    content_type: &str,
    headers: &HeaderMap,
    body: &[u8]
) -> Result<Vec<u8>, FastcgiError>
Available on crate feature kvarn-fastcgi-client only.