Product Reviews Shortcode - only works on single-product template

functions.php

/*========================================================================
3 Column Reviews shortcode - can only be used on single product pages
https://ginastricklind.com/how-to-create-a-product-reviews-shortcode-query/
========================================================================*/
add_shortcode( 'display_latest_reviews', 'gs_display_latest_reviews' );
function gs_display_latest_reviews() {

  if( is_product() ) {
    global $product;
    $id = $product->id;
    $args = array (
      'post_type' => 'product',
      'post_id'   => $id,
      'orderby'   => 'commment_date',
      'order'     => DESC,
      'number'		=> '3',
    );
    $comments = get_comments( $args );

    ob_start();
    ?>

    <div id="gs-reviews">
        <ul class="review-list">
            <?php $list = wp_list_comments( array( 'callback' => 'woocommerce_comments' ), $comments); ?>
        </ul>
    </div>

    <?
    $output = ob_get_contents();
    ob_get_clean();

    return $output;

  } else {
    return 'shortcode must be used on a single product view';
  }

}