works for: localhost:3000/api/todo

src/index.ts

 import express from 'express';
 import { json } from 'body-parser';
+import { todoRouter } from './routes/todo'
 
 const app = express()
 app.use(json())
+app.use(todoRouter)
 
 app.listen(3000, () => {
     console.log('server is listening on port 3000')

src/routes/todo.ts

-import express from 'express'
+import express, { Request, Response} from 'express'
 
 const router = express.Router()
 
-router.get('/api/todo', (req, res) => {
+router.get('/api/todo', [], (req: Request, res: Response) => {
     return res.send('the todo')
 })