❤️ Laravel : (5.5) : Allow login using username or email

LoginController.php

// in app/Http/Controllers/Auth/LoginController.php
<?php


   /*
    * code ...
    */

    use AuthenticatesUsers;
    protected function credentials(Request $request)
    {
        $login = request()->input('email'); 

            // Check whether username or email is being used
            $field = filter_var($login, FILTER_VALIDATE_EMAIL) ? 'email' : 'username'; 
            return [ 
            $field    => $request->get('email'), 
            'password' => $request->password
            ];
    } 

    /*
    * code ...
    */
?>