How do I solve this parse error: "syntax error, unexpected 'as' (T_AS)"?

When I run command $ php artisan serve, I got this error:

[Symfony\Component\Debug\Exception\FatalErrorException] syntax error, unexpected 'as' (T_AS)

Route::group(['prefix' => 'admin'], function() {

    Route::get('/', [ 'as' => 'admin.login', 'uses' => 'Admin\AuthController@getLogin' ]);
    Route::post('/login', [ 'as' => 'admin.checkLogin', 'uses' => 'Admin\AuthController@checkLogin' ]);
    Route::get('/logout', [ 'as' => 'admin.logout', 'uses' => 'Admin\AuthController@getLogout' ]);

    Route::group(['middleware' => 'auth'], function() {

        Route::get('/dashboard', function(){
            return view('admin::user.dashboard');
        });

        Route::get('/users', [ 'as' => 'user.index', 'uses' => 'UserController@index' ]);

    });
});

via Chebli Mohamed