Add custom product navigation to Storefront Child Theme in WordPress

add_action( 'storefront_single_post', 'ATK_custom_post_nav', 5 );
// Note: These are reversed to navigate to previous on left
function ATK_custom_post_nav() {
   echo get_previous_post_link('%link',  '<span class="next-post-link"><i class="fas fa-angle-right"></i></span>');
   echo get_next_post_link('%link',  '<span class="previous-post-link"><i class="fas fa-angle-left"></i></span>');

}