You want to call any registered shutdown functions directly.
You're exiting your Laravel application in a non-standard way, and want to call any shutdown callbacks that have been registered with your application.
You can call
App::shutdown() without any arguments to automatically call what's registered.
// Call registered callbacks App::shutdown();
This is non-standard.
Calling this method directly is not part of the standard request lifecycle.
Also, note that calling
App::shutdown() does not actually exit your application, it only calls the registered shutdown callbacks.