Exclude current post for custom post type

Question

What I need: show random post except current post for custom post type Question

In below codes, the exclusion doesn't works. It simply show any post including current post.

<?php
    $my_query = new WP_Query( array('showposts' => '8', 'post_type' => 'question', 'post__not_in' => array( $post->ID ), 'orderby' => 'rand'));
    while ( $my_query->have_posts() ) : $my_query->the_post(); ?>
    <a href="<?php the_permalink(); ?>"><?php the_title() ?></a><br>
<?php endwhile; ?>

If I change the Question to be Page, it works for Page. If remove the Question, it works for Post.

I guess it must be something I missed if I want to make it works for custom post type

Update:

Previously I wrote Question now changed to question, but still results the same

Answer 1

You should use get_queried_object() or get_queried_object_id() to get the current custom post's ID. IMO get_queried_object() is a better choice here as you can conditionaly check for the post type also. Try this

function wpse258217_random_posts() {

    $obj = get_queried_object();

    if ( $obj->post_type === 'question' ) {
        $postid = $obj->ID;

        $my_query = new WP_Query( array('showposts' => '8', 'post_type' => 'question', 'post__not_in' => array( $postid ), 'orderby' => 'rand'));

        //Execute the loop here
    }

}