请问我怎么将原来的Auth功能 从验证 邮箱和密码 改成验证 用户名和密码？

<?php namespace App\Http\Controllers\Auth;



use App\Http\Controllers\Controller;

use Illuminate\Contracts\Auth\Guard;

use Illuminate\Contracts\Auth\Registrar;

use Illuminate\Foundation\Auth\AuthenticatesAndRegistersUsers;



class AuthController extends Controller {





use AuthenticatesAndRegistersUsers;



public function __construct(Guard $auth, Registrar $registrar)

{

    $this->auth = $auth;

    $this->registrar = $registrar;



    $this->middleware('guest', ['except' => 'getLogout']);

}



}