Add A "Proceed To Checkout" Button Under the "Add To Cart" Button on Single Product Page

proceed_to_checkout.php

/**
 * Adds a "Proceed To Checkout" button underneath the "Add To Cart" button
 * @author: CJ Andrew (cjwebstudio)
 */
 
 add_action('woocommerce_after_add_to_cart_form','proceed_to_checkout');
 
 function proceed_to_checkout(){
  global $woocommerce;
  $checkout_url = $woocommerce->cart->get_checkout_url();
  
    echo '<a href="'. $checkout_url .'" class="button">Proceed to Checkout</a>';
 }