Functions.php in child theme not working

Hello,
I wanted to add some code to my child theme’s functions.php in order to redirect visitors to the login page.
When i use the code in my main theme’s functions.php it works properly. but when i try it with the child theme, it seems that the code is simply ignored.

<?php
if( (!is_user_logged_in()) && ($GLOBALS['pagenow'] !== 'wp-login.php')  ) {
  wp_redirect('https://xxxxxxxxxxx.com/wp-login.php');
}
?>

So does anyone know how to fix this little issue? ??