Laravel：用户在会话过期后注销

I'm using Laravel 5.5 and the regular provided authentication.

Situation: The user leaves his computer for 2 hours (the default session timeout) and before leaving the office, he clicks on Logout.

Problem: The user gets the following error:

The page has expired due to inactivity. Please refresh and try again.

Refreshing the page has no effect. The same message is displayed again.

With Laravel 5.4, I had the following error:

TokenMismatchException in VerifyCsrfToken.php (line 68)

The link for logout is in the layout app.blade.php and hasn't been changed:

<li>
    <a href="{{ route('logout') }}"
       onclick="event.preventDefault();
                document.getElementById('logout-form').submit();">
        <span class="glyphicon glyphicon-off"></span>
        Logout
    </a>

    <form id="logout-form" action="{{ route('logout') }}" method="POST" style="display: none;">
        {{ csrf_field() }}
    </form>
</li>

Question How can I avoid the csrf validation when user clicks on logout?

I've just added an exception in App\Http\Middleware\VerifyCsrfToken.php

/**
 * The URIs that should be excluded from CSRF verification.
 *
 * @var array
 */
 protected $except = [
    'logout'
 ];

Ajay Deepak Kumar and Omisakin Oluwatobi are right. This makes the website vulnerable.