Fetch Handler
 Background
Incoming HTTP requests to a Worker are passed to the fetch() handler as a Request object. To respond to the request with a response, return a Response object:
export default {	async fetch(request, env, ctx) {		return new Response('Hello World!');	},
};
 Parameters
requestRequest- The incoming HTTP request.
 
envobject- The bindings available to the Worker. As long as the environment has not changed, the same object (equal by identity) may be passed to multiple requests.
 
ctx.waitUntil(promisePromise):void- Refer to 
waitUntil. 
- Refer to 
 ctx.passThroughOnException():void- Refer to 
passThroughOnException. 
- Refer to