woocommerce_update_shipping_on_postcode_change.php

<script type="text/javascript">
jQuery( 'document' ).ready( function ($) {
    $('#billing_postcode').on( 'focusout', function() {
        $(this).trigger('update_checkout');
    });
});
</script>

<?php
function mg_update_order_review_on_checkout( $post_data ) {
    WC()->cart->calculate_shipping();
    return;
}
add_action( 'woocommerce_checkout_update_order_review', 'mg_update_order_review_on_checkout', 10 );