returning redirect from parent's function.

Hi, I want to make simple authentication checking method in BaseController.php so it can be accessed by another controller like this:

PHP Code:

protected function mustLoggedIn()
{
    if (is_null($this->session->get('logged_in'))) {
        $this->session->setFlashdata(['error' => 'Maaf, anda harus login dulu']);
        return redirect()->to('/login');
        exit();
    }
} 


then accessed like this:

PHP Code:

public function beranda()
{
    $this->mustLoggedIn();
    return view('siswa/beranda');
} 


but it didn't work in CI4. Is my method wrong?
How to implement login check like that in CI4?