/**
 * Implements hook_menu_site_status_alter().
 */
function {{ machine_name }}_menu_site_status_alter(&$menu_site_status, $path) {
  // Allow access to my_module/authentication even if site is in offline mode.
  if ($menu_site_status == MENU_SITE_OFFLINE && user_is_anonymous() && $path == 'my_module/authentication') {
    $menu_site_status = MENU_SITE_ONLINE;
  }
}