Method [username] does not exist at login when upgrade from Laravel 5.2 to 5.3

After I recently upgraded Laravel from 5.2 to 5.3, I cannot login in to my app.

For a simple login I receive: BadMethodCallException in app/vendor/laravel/framework/src/Illuminate/Routing/Controller.php line 82 with the message Method [username] does not exist

I see the cause is from ThrottlesLogins. If I remove the Trait called ThrottlesLogins from my AuthController it will work.

The method [username] is from the ThrottlesLogins Trait at

protected function throttleKey(Request $request) { return Str::lower($request->input($this->username())).'|'.$request->ip(); }

via Chebli Mohamed