public function set($fx = [], $args = null)
    {
        if (!is_callable($fx)) {
            throw new Exception('Error: Need to pass a callable function to Loader::set()');
        }

        $this->cb->set(function () use ($fx) {
            call_user_func($fx, $this);
            $this->app->terminate($this->renderJSON());
        });

        return $this;
    }