dm-v3.7in6.com/application/admin/controller/Code.php

<?php

namespace app\admin\controller;

use app\common\controller\Backend;
use \think\Session;
use \think\Db;

class Code extends Backend{

    public function index(){
        $list = Db::connect('mongodb');
//        halt($list);
    }
    public function add()
    {

    }
}