Undefined index: password Laravel 5.5 - logging

In my database password column name is "new_password". then when I try to log, it says Undefined index: password. But if password column name is "password" it works properly. I need to use previous column name.

How can I fix this?

$credentials = array(
        'user_name'    => Input::get('username'),
        'new_password' => Input::get('password')
);

$user = Auth::attempt($credentials);

via Chebli Mohamed