WordPress loop with woocommerce product category

index.php

<div class="promo_area">
    <?php
    global $post;
    $args = array( 'posts_per_page' => 6, 'post_type'=> 'product', 'order' => 'DESC', 'product_cat' => 'promo', );
    $myposts = get_posts( $args );
    foreach( $myposts as $post ) : setup_postdata($post); ?>
        <div class="col-md-4 col-sm-6 col-xs-12">
            <div class="promo_single">
                <div class="grid">
                    <figure class="promo_offers">
                        <?php the_post_thumbnail();?>
                            <figcaption>
                                <h2><?php the_title(); ?></h2>
                                    <?php the_excerpt(); ?>                                       
                                <a href="<?php the_permalink(); ?>">View more</a>
                            </figcaption>           
                    </figure>
                </div>
            </div>
        </div>
    <?php endforeach; ?>
</div>