Serverless + sls-http + koa example

router.ts

// written typescript
import { APIGatewayEvent, Context, Handler } from "aws-lambda";

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

import serverlessHttp from "serverless-http";

// for serverless offline
export interface SlsExtendableOfflineEvent extends APIGatewayEvent {
  isOffline?: boolean;
}

const app = new Koa();
const router = new Router({ prefix: "/prefix" });

// set simple server middleware or use koa-logger
app.use(async (ctx, next) => {
    try {
      console.log(`(${ctx.method})[${ctx.url}] Requested`);
      ctx.set("Access-Control-Allow-Credentials", "true");
      ctx.set(
        "Access-Control-Allow-Origin",
        "some cors access domain"
      );
      await next();
    } catch (err) {
      ctx.status = err.status || 500;
      ctx.body = 
        process.env === "development" ? err.message : "internal server error"
      ctx.app.emit("error", err, ctx);
    }
  });

app.on("error", (err, ctx) => {
  console.error(`(${ctx.method})[${ctx.url}] Got An Error:`, err, ctx);
  console.error(err.stack);
});

router.get("/", async ctx => {
  // Some business logic

  ctx.status = 200;
  ctx.body = "get success";
});

app.use(router.routes());

const slsApp = serverlessHttp(app, {
  request(req: Koa.SlsHttpIncomingMsg, event: SlsExtendableOfflineEvent) {
    if (!event.isOffline) {
      // remove CDN Prefix if exists, for sls-offline (ex. /route/prefix)
      const cdnPrefix = req.url.split(this.prefix)[0];
      req.url = req.url.replace(cdnPrefix, "");
    }
    // pass lambda's requestContext for auth, etc.
    req.context = event.requestContext;
  }
});

export const handler: Handler = async (
  event: APIGatewayEvent,
  context: Context
) => {
  return slsApp(event, context);
};