Laravel: Specify Auth::guard() by Middleware?

In my application I have a separate guard for administrator.

I have created a helper function like this:

function admin_auth()
{
        return \Illuminate\Support\Facades\Auth::guard(config('admin.auth.guard'));
} 

and I use this method in my controllers and blade files for example like this:

if (admin_auth()->attempt($credentials, $request->has('remember'))) {
    return $this->sendLoginResponse($request);
}

or like this

<p></p>

All controller and blade files from my admin dashboard are accessible under the route

Route::group(['prefix' => 'admin'], function () {
 //...
}

My question is: Is it possible that if and only if I call a controller or blade file with prefix /admin in the route, that the function Auth() will call admin_auth() ?

So that I could simplify my code to

<p></p>

I couldn't find that in the docs but I thought maybe this is possible via middleware?

via Chebli Mohamed