Generated Vue-Cli project: error using VueRouter

[tom-cosmol]

I have this Problem:
The generated vue example as generated with vue create client (vue2)

The original example works,
but when I define even one VueRouter, I get the error
Uncaught TypeError: bootstrap_vue__WEBPACK_IMPORTED_MODULE_2__.default is not a constructor,
see below.
I have tried everything possible and searched everywhere,
although I explicitly use vue 2;
but using the VueRouter remains a problem,

There is no difference if I use the router
_new Vue({
my router,
render: h => h(App),
}).$mount('#app')
or not
new Vue({
render: h => h(App),
}).$mount('#app')

vue create client => vue 2

Default ([Vue 2] babel, eslint)

Versions in the generated project as specified on https://bootstrap-vue.org/:
npm list:
[email protected] D:\sbox\web\ResourceLockerProject\test3\client
+-- @babel/[email protected]
+-- @babel/[email protected]
+-- @babel/[email protected]
+-- @vue/[email protected]
+-- @vue/[email protected]
+-- @vue/[email protected]
+-- @vue/[email protected]
+-- @vue/[email protected]
+-- [email protected]
+-- [email protected]
+-- [email protected]
+-- [email protected]
+-- [email protected]
+-- [email protected]
+-- [email protected]
+-- [email protected]
+-- [email protected]
+-- [email protected]
+-- [email protected]
+-- [email protected]
`-- [email protected]

generated main.js, modified:

import Vue from 'vue'
import App from './App.vue'
Vue.config.productionTip = false

// additional lines to generated example: start
import VueRouter from 'bootstrap-vue'
const routes = [
  {
      path: '/',
      component: App
  }
]
const my_router = new VueRouter({
   routes
 });
Vue.use(my_router)** 
// additional lines to generated example: end_

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

Browser => Blank site with error message in the console:

Uncaught TypeError: bootstrap_vue__WEBPACK_IMPORTED_MODULE_2__.default is not a constructor
main.js:14
js app.js:175
webpack_require app.js:257
webpack_exports app.js:1379
O app.js:303
app.js:1380
app.js:1382

[Hiws]

This doesn't look quite right

import VueRouter from 'bootstrap-vue'

[tom-cosmol]

thank you very much, that's it !
vue add router and: import VueRouter from 'vue-router'