User immediately logged out after submitting a form via POST route

Question

Every time a form is submitted, the user is immediately logged out. I have tried to start making my application again from scratch or even using Laravel built-in Authentication from make:auth but the problem still persists.

Currently I'm using Laravel 5.6.33

these are my code : web.php

<?php

    Route::get('/', 'HomeController@index')->name('home');


    Route::get('/posts','PostController@index');
    Route::post('/posts','PostController@store');
    Route::get('/posts/create','PostController@create');
    Route::get('/posts/{id}/reply','ReplyController@create');
    Route::post('/posts/{id}/reply','ReplyController@store');


    Route::get('/register','RegisterController@create')->name('register.create');
    Route::post('/register','RegisterController@store')->name('register');
    Route::get('/login','LoginController@create')->name('login');
    Route::post('/login','LoginController@store')->name('login.store');
    Route::get('/password/reset','LoginController@reset')->name('password.request');

    Route::post('/logout','LoginController@destroy')->name('logout');

And, in my PostController.php I put middleware

public function __construct(){
    $this->middleware('auth')->except(['index','store']);
}

Where index is for listing my posts, and store is for save new post. there is also has function create to show the post form.