Lae/app/Http/Controllers/Admin/AuthController.php

<?php

namespace App\Http\Controllers\Admin;

use App\Http\Controllers\Controller;
use Illuminate\Http\Request;

class AuthController extends Controller
{
    //

    public function index()
    {
        // if not authed

        if (!auth('admin')->check()) {
            return view('admin.login');
        } else {
            return redirect()->route('admin.index');
        }
    }

    public function login(Request $request)
    {
        if (auth('admin')->attempt($request->only('email', 'password'))) {
            return redirect()->route('admin.index');
        } else {
            return redirect()->route('admin.login')->with('error', 'Invalid credentials');
        }
    }
}