Why the error runs – Uncaught SyntaxError: The requested module ‘/src/router/index.js’ does not provide an export named ‘default’ at main.js vue?

At vite vue runs the error – Why the error runs – Uncaught SyntaxError: The requested module ‘/src/router/index.js’ does not provide an export named ‘default’ at main.js vue ? What is wrong ?

https://stackblitz.com/edit/vue3-vite-starter-ywq59j?file=package.json,src%2Fcomponents%2FFooter.vue,src%2Fcomponents%2FHeader.vue,src%2Fcomponents%2FMain.vue,src%2Fcomponents%2FNotMain.vue,src%2Fviews%2FHome.vue,src%2Fviews%2FShops.vue,src%2FApp.vue,src%2Fmain.js,public%2Ffavicon.ico

// main.js

import { createApp } from 'vue'
import 'bootstrap/dist/css/bootstrap.css'
import 'bootstrap/dist/js/bootstrap.js'
import App from './App.vue'
import router from './router'

const app = createApp(App)

app.use(router)

app.mount('#app')