Custom text above add to cart based on shipping class - WooCommerce

gistfile1.txt

function custom_text_per_shipping_class() {
  global $product;
$product = wc_get_product();
$shipping_class = $product->get_shipping_class();

      if ($shipping_class == 'a'){
        echo "a";
      } elseif ($shipping_class == 'b') {
        echo "b";
      } else { 
        echo "I am not in the above shipping classes";

      }

  }
add_action( 'woocommerce_before_add_to_cart_form', 'custom_text_per_shipping_class', 20 );