Put Your Site in Maintenance Mode Using Function.php in WordPress :

<script>
function wp_maintenance_mode(){
if(!current_user_can('edit_themes') || !is_user_logged_in()){
wp_die('Maintenance, please come back soon.', 'Maintenance - please come back soon.', array('response' => '503'));
}
}
add_action('get_header', 'wp_maintenance_mode');
</script>
And Save your File. Than See Your Site Home Page Give Your Maintenance Message.