'post',
'posts_per_page' => 1,
'post_status' => 'publish',
'post__not_in' => array( get_the_ID() ),
'orderby' => 'rand',
);
$related = new WP_Query( $related_args );
if( $related->have_posts() ) :
while( $related->have_posts() ): $related->the_post();
?>