#Fix the construct spelling

You need to make it public function __construct(){}, and check your construct spelling, its obvious but you might missed it in first place.

Public access modifier is also needed. Try that and see the outcome. Check here to confirm it.

1. Check spelling
2. Make the constructor public
3. Remove dd('die'), I've run the code and that's the one blocking, because of the flow of the code.

#Why remove dd('die')

The idea of auth is to prevent unauthenticated user from seeing the page. By using dd('die'), you just show the whole page to the unauthenticated user! The flow of the code is interrupted!

public function __construct(){

    $this->middleware('auth');
}

#How to solve?

Use proper 'return' technique, such as this code, or add that dd('die') into the index function:

    public function index(){
    	return view('index.blade.php');
    }

Or if it is not working, do this workaround.

Check if auth is registered

Have you register your 'auth' middleware inside App\Kernel?

    protected $routeMiddleware = [
    'auth' => \Illuminate\Auth\Middleware\Authenticate::class,
    ....
    ];

https://laravel.com/docs/5.3/middleware#registering-middleware

Route casting directly from web.php

Try to use the normal way to cast your middleware, by casting it inside your web.php and see if it is working first hand:

Route::get('/your-route', 'AdvertController@index')->middleware('auth');

Cheers.