Angular5和Bootstrap4 -无法将最后一个菜单项与右侧对齐

<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@4.0.0/dist/css/bootstrap.min.css">

<nav class="navbar navbar-expand-lg navbar-light bg-light">
  <div class="collapse navbar-collapse" id="navbarSupportedContent">
    <ul class="navbar-nav mr-auto">
      <li class="nav-item">
        <a class="nav-link" href="#">菜单项1</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">菜单项2</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">菜单项3</a>
      </li>
      <li class="nav-item ml-auto">
        <a class="nav-link" href="#">最后一个菜单项</a>
      </li>
    </ul>
  </div>
</nav>