Custom post template makes my wordpress crash - wordpress

Question

I have created a custom post type "toornament" in my wp.
I have done a single-toornament.php in my plugin.
When i require it in my index.php, i have a fatal error...
Maybe it can be a pot configurating erro ? I give you the code below.
Do you know where it can be from ?
<?php
function toornament_post() {
// Set UI labels for Custom Post Type
$labels = array(
'name' => _x( 'Toornaments', 'Post Type General Name', 'twentytwenty' ),
'singular_name' => _x( 'Toornament', 'Post Type Singular Name', 'twentytwenty' ),
'menu_name' => __( 'Toornaments', 'twentytwenty' ),
'parent_item_colon' => __( 'Parent Toornament', 'twentytwenty' ),
'all_items' => __( 'All Toornaments', 'twentytwenty' ),
'view_item' => __( 'View Toornament', 'twentytwenty' ),
'add_new_item' => __( 'Add New Toornament', 'twentytwenty' ),
'add_new' => __( 'Add New', 'twentytwenty' ),
'edit_item' => __( 'Edit Toornament', 'twentytwenty' ),
'update_item' => __( 'Update Toornament', 'twentytwenty' ),
'search_items' => __( 'Search Toornament', 'twentytwenty' ),
'not_found' => __( 'Not Found', 'twentytwenty' ),
'not_found_in_trash' => __( 'Not found in Trash', 'twentytwenty' ),
);
// Set other options for Custom Post Type
$args = array(
'label' => __( 'Toornament', 'twentytwenty' ),
'description' => __( 'Toornament information et inscription', 'twentytwenty' ),
'labels' => $labels,
// Features this CPT supports in Post Editor
'supports' => array( 'title', 'editor', 'excerpt', 'author', 'thumbnail', 'comments', 'revisions', 'custom-fields', ),
// You can associate this CPT with a taxonomy or custom taxonomy.
'taxonomies' => array( 'genres' ),
/* A hierarchical CPT is like Pages and can have
* Parent and child items. A non-hierarchical CPT
* is like Posts.
*/
'hierarchical' => false,
'public' => true,
'show_ui' => true,
'show_in_menu' => true,
'show_in_nav_menus' => true,
'show_in_admin_bar' => true,
'menu_position' => 5,
'can_export' => true,
'has_archive' => false,
'exclude_from_search' => false,
'publicly_queryable' => true,
'query_var' => 'toornament',
'capability_type' => 'post',
'show_in_rest' => true,
);
// Registering your Custom Post Type
register_post_type( 'toornament', $args );
}
I have add this :
function get_custom_post_type_template( $single_template ) {
global $post;
if ( 'toornament' === $post->post_type ) {
$single_template = dirname( __FILE__ ) . '/single-toornament.php';
}
return $single_template;
}
add_filter( 'single_template', 'get_custom_post_type_template' )

Answer 1

if you create single-{post-type}.php template you should not include it to the index.php
For adding a single template for your Custom Post Type there are two ways:
Copy it to your Child-Theme
hook it via single_template filter hook. here you will find how to do it
your code to create a new Custom Post Type from your question works.