nodeサーバーで発生するエラーを解決したい。

前提・実現したいこと

現在、Node.js, Vue.jsを用いてamazonのクローンサイトを開発しております。
そこでroutesディレクトリにowner.jsを実装し、ターミナルにてサーバーを立ち上げた際に以下のエラーが発生いたしました。

発生している問題・エラーメッセージ

terminal
1/Users/user/amazon/server/node_modules/express/lib/router/index.js:502
2  this.stack.push(layer);
3             ^
4
5TypeError: Cannot read property 'push' of undefined
6    at Function.route (/Users/user/amazon/server/node_modules/express/lib/router/index.js:502:14)
7    at Function.proto.(anonymous function) [as post] (/Users/user/amazon/server/node_modules/express/lib/router/index.js:509:22)
8    at Object.<anonymous> (/Users/user/amazon/server/routes/owner.js:5:8)
9    at Module._compile (internal/modules/cjs/loader.js:778:30)
10    at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
11    at Module.load (internal/modules/cjs/loader.js:653:32)
12    at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
13    at Function.Module._load (internal/modules/cjs/loader.js:585:3)
14    at Module.require (internal/modules/cjs/loader.js:692:17)
15    at require (internal/modules/cjs/helpers.js:25:18)
16    at Object.<anonymous> (/Users/user/amazon/server/server.js:33:21)
17    at Module._compile (internal/modules/cjs/loader.js:778:30)
18    at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
19    at Module.load (internal/modules/cjs/loader.js:653:32)
20    at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
21    at Function.Module._load (internal/modules/cjs/loader.js:585:3)
22[nodemon] app crashed - waiting for file changes before starting...

該当のソースコード

routesownerjs
1const router = require('express').Router
2const Owner = require('../models/owner')
3
4// POST api
5router.post('/owners', async (req, res) => {
6  try {
7    let owner = new Owner()
8    owner.name = req.body.name
9    owner.about = req.body.about
10    await owner.save()
11
12    res.json({
13      success: true,
14      message: 'Successfully created a new owner'
15    })
16  } catch (err) {
17    res.status(500).json({
18      success: false,
19      message: err.message
20    })
21  }
22})
23
24// GET api
25router.get('/owners', async (req, res) => {
26  try {
27    let owners = await Owner.find()
28
29    res.json({
30      owners: owners
31    })
32  } catch (err) {
33    res.status(500).json({
34      success: false,
35      message: err.message
36    })
37  }
38})
39
40module.exports = router
41

試したこと

こちらのサイトを参考に、ターミナルにて$ vi ~/amazon/server/node_modules/express/lib/router/index.jsを実行し、
import { Router } from 'express';

const router = Router();

router.get('/', (req, res) => {
return res.send(req.context.models.users[req.context.me.id]);
});

こちらを追加で記述しても解決には至りませんでした。

補足情報（package.json）

{
"name": "server.js",
"version": "1.0.0",
"description": "",
"scripts": {
"test": "echo "Error: no test specified" && exit 1"
},
"author": "",
"license": "ISC",
"dependencies": {
"aws-sdk": "^2.580.0",
"body-parser": "^1.19.0",
"dotenv": "^8.2.0",
"express": "^4.17.1",
"mongodb": "^3.3.5",
"mongoose": "^5.7.12",
"morgan": "^1.9.1",
"multer": "^1.4.2",
"multer-s3": "^2.9.0",
"npm": "^6.13.1"
}
}