public static function onMessage(string $client_id, $message)
{
    try {
        $msg = json_decode($message);
        $op = $msg->op ?? false;

        $controller = new TestController();
        if (method_exists($controller, $op)) {
            $request = new Request($msg['data']);
            $res = $controller->$op($request);
            // ....
        }
    } catch (Throwable $e) {
        echo "Error in onMessage: " . $e->getMessage() . "\n";
    }
}