koa2 安装

npm i koa koa-router

npm i @types/koa @types/koa-router --save-dev

server.ts

import Koa from "koa";
import Router from "koa-router";

const app = new Koa();
const router = new Router();

// Todo: if the path is '/*', the server will crash at lint 8
router.get("/", async (ctx) => {
  ctx.body = "Hello World!";
});

app.use(router.routes());

app.listen(3000);

console.log("Server running on port 3000");