function davoil_maintenance_mode() {
    if ( ! current_user_can( 'manage_options' ) ) {
        wp_die(
            '<h1>Site temporarily unavailable</h1><p>We will be back soon.</p>',
            'Temporarily unavailable',
            array( 'response' => 503 )
        );
    }
}
add_action( 'template_redirect', 'davoil_maintenance_mode' );<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="https://www.davoilinc.com/wp-sitemap-index.xsl" ?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"><sitemap><loc>https://www.davoilinc.com/wp-sitemap-posts-page-1.xml</loc></sitemap></sitemapindex>