Navbar Bootstrap collapse is not working in Vue

I started a new project with Vue and Bootstrap, but when using Bootstrap navbar in Vue navbar-collapse does not work, follow the code.

App.vue

<template>
  <div id="app">

    <b-navbar toggleable="md" type="dark" variant="info">

      <b-navbar-toggle target="nav_collapse"></b-navbar-toggle>

      <b-navbar-brand href="#">NavBar</b-navbar-brand>

      <b-collapse is-nav id="nav_collapse">

        <b-navbar-nav>
          <b-nav-item href="#">Link</b-nav-item>
          <b-nav-item href="#" disabled>Disabled</b-nav-item>
        </b-navbar-nav>

        <!-- Right aligned nav items -->
        <b-navbar-nav class="ml-auto">

          <b-nav-form>
            <b-form-input size="sm" class="mr-sm-2" type="text" placeholder="Search"/>
            <b-button size="sm" class="my-2 my-sm-0" type="submit">Search</b-button>
          </b-nav-form>

          <b-nav-item-dropdown text="Lang" right>
            <b-dropdown-item href="#">EN</b-dropdown-item>
            <b-dropdown-item href="#">ES</b-dropdown-item>
            <b-dropdown-item href="#">RU</b-dropdown-item>
            <b-dropdown-item href="#">FA</b-dropdown-item>
          </b-nav-item-dropdown>

          <b-nav-item-dropdown right>
            <!-- Using button-content slot -->
            <template slot="button-content">
              <em>User</em>
            </template>
            <b-dropdown-item href="#">Profile</b-dropdown-item>
            <b-dropdown-item href="#">Signout</b-dropdown-item>
          </b-nav-item-dropdown>
        </b-navbar-nav>
      </b-collapse>
    </b-navbar>
    <!-- navbar-1.vue -->
  </div>
</template>
<script>
  export default {
    name: 'app',
    data () {
      return {
        msg: 'Header',
        home: 'Home'
      }
    }
  }
</script>

<style>
  ...
</style>

And in main.js

import Vue from 'vue'
import BootstrapVue from "bootstrap-vue"
import App from './App.vue'
import "bootstrap/dist/css/bootstrap.min.css"
import "bootstrap-vue/dist/bootstrap-vue.css"

Vue.use(BootstrapVue)

new Vue({
  el: '#app',
  render: h => h(App)
})