Can't call Auth::user() on controller's constructor

See here:

Session In The Constructor

In previous versions of Laravel, you could access session variables or the authenticated user in your controller's constructor. This was never intended to be an explicit feature of the framework. In Laravel 5.3, you can't access the session or authenticated user in your controller's constructor because the middleware has not run yet.

As an alternative, you may define a Closure based middleware directly in your controller's constructor. Before using this feature, make sure that your application is running Laravel 5.3.4 or above:

<?php

namespace App\Http\Controllers;

use App\User;
use Illuminate\Support\Facades\Auth;
use App\Http\Controllers\Controller;

class ProjectController extends Controller
{
    /**
     * All of the current user's projects.
     */
    protected $projects;

    /**
     * Create a new controller instance.
     *
     * @return void
     */
    public function __construct()
    {
        $this->middleware(function ($request, $next) {
            $this->projects = Auth::user()->projects;

            return $next($request);
        });
    }
}

Of course, you may also access the request session data or authenticated user by type-hinting the Illuminate\Http\Request class on your controller action:

/**
 * Show all of the projects for the current user.
 *
 * @param  \Illuminate\Http\Request  $request
 * @return Response
 */
public function index(Request $request)
{
    $projects = $request->user()->projects;

    $value = $request->session()->get('key');

    //
}