Laravel 5.6在控制器构造函数中访问auth()->user()？

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;

class UserController extends Controller
{
    protected $user;

    public function __construct()
    {
        $this->middleware(function ($request, $next) {
            $this->user = auth()->user();
            return $next($request);
        });
    }

    public function index()
    {
        // 使用$this->user访问当前已认证用户的信息
        if ($this->user) {
            // 执行相应的操作
        } else {
            // 用户未认证的处理逻辑
        }
    }
}