Product Out Of Stock given custom message in woocommerce

When product 'out of stock' given custom message in woocommerce plugin.

Using custom plugin file following hook not working on plugin file.

add_action('woocommerce_single_product_summary','function_xyz', 10, 2 );

Above hook working on theme function.php perfectly.

Suggest me. Using plugin file any hook that can i add custom message when product out of stock.

Thanks.

via Chebli Mohamed