PHP8 problems

Hi, im using ci4 and working well other php versions but i have problem with php8.
first problems solved with here: https://forum.codeigniter.com/thread-78146.html
and now my route not working. 

PHP Code:

$routes->get('/', 'IndexController::index'); 


and getting this error: Controller method is not found: index
so if i do my index function static route working like this. But i cant all functions to static please help.

PHP Code:

<?php namespace App\Controllers;
class IndexController extends BaseController
{
  public function __construct(){
    var_dump("TEST");
  }
public static function index()
{
return view('welcome_message');
}
//--------------------------------------------------------------------

}