Give me a comment about woocommerce.

I made a custom item field for woocommerce order. on wp_woocommerce_order_itemmeta, I added meta_key '_line_pinlist' using wc_add_order_item_meta( $item["id"], '_line_pinlist', $meta_pin_list ) I added this function on update_status() of class-wc-order.php. this function is called on if ( 'completed' == $new_status->slug ) { } flow. when I click 'complete' button _line_pinlist was wrote on database with this function call. sample: '383', '46', '_line_pinlist', '13906549391125710', '46' (wp_woocommerce_order_itemmeta) but when I receive email this field is empty. on [login to view URL], I already added one more column like <td style="text-align:left; vertical-align:middle; border: 1px solid #eee;"><?php echo $item['line_pinlist']; ?></td> when I put the debug at the end of line like <tr> <td colspan="4"> <?php echo var_dump($items);?> </td> </tr> it doesn't contain any line_pinlist. (but db field is already filled up) I don't know well about woocommerce function lifecycle. maybe, after email sending out, status update called or $items is cached before status update. this issue eating my time. anyone who knows well about woocommerce, please teach me how to solve this issue.