protected function registerHttplug()
    {
        $this->app->singleton('httplug', function ($app) {
            return new HttplugManager($app);
        });
        $this->app->alias('httplug', HttplugManager::class);

        $this->app->singleton('httplug.default', function ($app) {
            return $app['httplug']->driver();
        });
    }