Programmatically add product to cart

functions.php

<?php
/*
Plugin Name: Programmatically add product to cart
Plugin URI: https://www.webmenedzser.hu
Description: Add a product to the cart programmatically if the user role is subscriber
Version: 1.0
Author: Radics Ottó
Author URI: https://www.webmenedzser.hu
License: GPLv3
*/

function add_product_to_cart_programmatically() {
    if (current_user_can('subscriber')) {
        $productID = 39;

        $productCartID = WC()->cart->generate_cart_id( $productID );
        $inCart = WC()->cart->find_product_in_cart( $productCartID );

        if ( !$inCart ) {
            WC()->cart->add_to_cart( $productID );
        }
    }
}
add_action( 'template_redirect', 'add_product_to_cart_programmatically', 10, 0 );