add custom post type

/**
 *
 * add custom post type
 *
 */
function my_custom_post_product() {
  $labels = array(
    'name'               => _x( 'Products', 'post type general name' ),
    'singular_name'      => _x( 'Product', 'post type singular name' ),
    'add_new'            => _x( 'Add New', 'book' ),
    'add_new_item'       => __( 'Add New Product' ),
    'edit_item'          => __( 'Edit Product' ),
    'new_item'           => __( 'New Product' ),
    'all_items'          => __( 'All Products' ),
    'view_item'          => __( 'View Product' ),
    'search_items'       => __( 'Search Products' ),
    'not_found'          => __( 'No products found' ),
    'not_found_in_trash' => __( 'No products found in the Trash' ),
    'parent_item_colon'  => '',
    'menu_name'          => 'Products'
  );
  $args = array(
    'labels'        => $labels,
    'description'   => 'Holds our products and product specific data',
    'public'        => true,
    //'menu_position' => 5,
    'supports'      => array( 'title', 'editor', 'thumbnail', 'excerpt', 'comments', 'custom-fields' ),
    'taxonomies'    =>array('category','post_tag', 'projects'),
    'has_archive'   => true,
    'show_in_rest' => true
  );
  register_post_type( 'product', $args );
}
add_action( 'init', 'my_custom_post_product' );


/** Code to get json output **/
add_action( 'init', 'add_anuncios_to_json_api', 30 );
function add_anuncios_to_json_api(){
    global $wp_post_types;
    $wp_post_types['product']->show_in_rest = true;
}

after that, you'll be able to list your posts from mydomain.com/wp-json/wp/v2/posttype_slug
in my case: mydomain.com/wp-json/wp/v2/myposttypename



/**code to add acf field in api**/
 add_action( 'rest_api_init', 'add_faculty_type_to_json' );
function add_faculty_type_to_json() {

    register_rest_field(
        'product', //the post type of your choice
        'book_file', //the name for your json element
        array(
            'get_callback'    => 'faculty_return_type', //the function that creates the content
        )
    );
}

// Return acf field staff_group
function faculty_return_type( $object, $field_name, $request ) {
    global $post;
    $faculty_type = get_field('book_file', $post->ID);
    //print_r($faculty_type);
    return $faculty_type['url']; //multiple selections are possible here but in this use case I only want the first one
}