Auth::user() not working laravel 8 code example

Example: how to change laravel 8 login credentials

//add below code to fortify service provider boot function
Fortify::authenticateUsing(function (LoginRequest $request) {
		    $user = User::where('user_name', $request->user_name);

		    if (
			    $user &&
			    Hash::check($request->password, $user->password)
		    ) {
			    return $user;
		    }
	    });
//and change username in fortify config 
'username' => 'user_name',