<?php
   wp_nav_menu([
      'menu'            => 'primary',
      'theme_location'  => 'primary',
      'container'       => 'div',
      'container_id'    => 'primary-nav',
      'container_class' => 'collapse navbar-collapse',
      'menu_id'         => 'main-menu',
      'menu_class'      => 'navbar-nav ml-auto',
      'depth'           => 3
   ]);