problem in laravel default Auth Controller

Hi guys,
I want to add arcaptcha to my own laravel project, in auth controller i got this error : 
```توکن ورود دیگر اعتبار ندارد```
i want to add arcaptcha check in my credentials method in LoginController
``` $credentials = Arr::add($credentials, 'arcaptcha-token', 'arcaptcha');`

i want to know where is my mistake.