WooCommerce add_action hook results in 500 error

by

Remove the = sign after your echo statement…

echo = "<p>Text Goes Here</p>";

…becomes

echo "<p>Text Goes Here</p>";

Final

 add_action( 'woocommerce_review_order_after_shipping', 'action_woocommerce_review_order_after_shipping');

function action_woocommerce_review_order_after_shipping( ) {
    echo "<p>Text Goes Here</p>";
}