继承Controller类之后报错

<?php

namespace app\admins\controller;

use think\Controller;

use Util\data\Sysdb;

class Test extends Controller

{

public function index(){

$this->db = new Sysdb;

$res = $this->db->table('admins')->field('id,username')->lists();

dump($res);

}

}

会显示该网页无法运作，去掉extends Controller就不会报这个错