Use middleware in lumen 5.1

I have in routes:

    $app->get('/', function () use ($app) {
    return $app->welcome();
});
$app->get('home', function () {
    return 'Bienvenido';
});

In ExampleMiddleware:

public function handle($request, Closure $next)
{
    //si se envia una variable year mayor a 18 redirige
    if($request->input('year') >= 18){
        return redirect('home');
    }
    return $next($request);
}

And in app:

$app->middleware([
    App\Http\Middleware\ExampleMiddleware::class
]);

But when going to link , I get the message:

Whoops, looks like something went wrong.