Get template part in wp nav menu

Question

I'm trying to add my own field to the menu using get_template_part. The problem is that my code is not working well because it is outside <ul id="primary-menu" class="nav-menu">

here is php:

<?php
$open_g = get_template_part('template/open_google_nav', false);
$items_wrap = '<ul id="%1$s" class="%2$s">%3$s';
$items_wrap .= sprintf( '<li id="item-google-nav">%1$s</li></ul>', $open_g );

    wp_nav_menu(
        array(
            'items_wrap' => $items_wrap,
            'theme_location' => 'desktop-menu',
            'menu_class'     => 'nav-menu',
            'menu_id'        => 'primary-menu',
            )
        );         
?>

Here is generated HTML from PHP

<nav id="primary-navigation" class="site-navigation primary-navigation" role="navigation">
"My template part"  --> Here is my template part
<div class="menu-glowne-menu-container">
    <ul id="primary-menu" class="nav-menu">
        <li id="menu-item-32" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-32"><a href="#"><span class="menu-item-description">Desc</span>Menu 1</a></li>
        <li id="menu-item-31" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-31"><a href="#"><span class="menu-item-description">Desc</span>Menu 2</a></li>
        <li id="menu-item-30" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-30"><a href="#"><span class="menu-item-description">Desc</span>Menu 3</a></li>
        <li id="item-google-nav">HERE SHOULD BE MY TEMPLATE PART</li>
    </ul>
</div>
</nav>

What am I doing wrong?