improvement: reduce serverless entry index code

Author: 郎永山

README.md

@@ -45,18 +45,16 @@ $ npm install tencent-serverless-http --save
 ```
 import { NestFactory } from '@nestjs/core';
 import { AppModule } from './app.module';
-import { Server } from 'http';
 import { ExpressAdapter } from '@nestjs/platform-express';
 import * as express from 'express';
-import { createServer } from 'tencent-serverless-http';
 
-export const bootstrapServer = async (): Promise<Server> => {
+export const createApp = async (): Promise<express.Express> => {
     const expressApp = express();
     const adapter = new ExpressAdapter(expressApp);
     const app = await NestFactory.create(AppModule, adapter);
     app.enableCors();
     await app.init();
-    return createServer(expressApp)
+    return expressApp
 }
 ```
 

lambda-handler.js

@@ -1,10 +1,11 @@
-const { proxy } = require('tencent-serverless-http')
+const { createServer, proxy } = require('tencent-serverless-http')
 
 let cachedServer
 module.exports.handler = async (event, context) => {
-  const { bootstrapServer } = require.fromParentEnvironment('./dist/index')
+  const { createApp } = require.fromParentEnvironment('./dist/index')
   if (!cachedServer) {
-    const server = await bootstrapServer()
+    const expressApp = await createApp()
+    const server = createServer(expressApp)
     cachedServer = server
     return proxy(server, event, context, 'PROMISE').promise
   } else {