message: docs(examples): Update multi_server example to use async await
diff: +#![feature(async_await)]
  #![deny(warnings)]
  extern crate hyper;
  extern crate pretty_env_logger;
  -use hyper::{Body, Response, Server};
  -use hyper::service::service_fn_ok;
  -use hyper::rt::{self, Future};
  +use hyper::{Body, Request, Response, Server};
  +use hyper::service::{service_fn, make_service_fn};
  +use futures_util::future::join;
  static INDEX1: &'static [u8] = b"The 1st service!";
  static INDEX2: &'static [u8] = b"The 2nd service!";
  -fn main() {
  +async fn index1(_: Request<Body>) -> Result<Response<Body>, hyper::Error> {
  + Ok(Response::new(Body::from(INDEX1)))
  +}
  +
  +async fn index2(_: Request<Body>) -> Result<Response<Body>, hyper::Error> {
  + Ok(Response::new(Body::from(INDEX2)))
  +}
  +
  +#[hyper::rt::main]
  +async fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
  pretty_env_logger::init();
  let addr1 = ([127, 0, 0, 1], 1337).into();
  let addr2 = ([127, 0, 0, 1], 1338).into();
  - rt::run(rt::lazy(move || {
  let srv1 = Server::bind(&addr1)
  - .serve(|| service_fn_ok(|_| Response::new(Body::from(INDEX1))))
  - .map_err(|e| eprintln!("server 1 error: {}", e));
  + .serve(make_service_fn(|_| {
  + async {
  + Ok::<_, hyper::Error>(service_fn(index1))
  + }
  + }));
  let srv2 = Server::bind(&addr2)
  - .serve(|| service_fn_ok(|_| Response::new(Body::from(INDEX2))))
  - .map_err(|e| eprintln!("server 2 error: {}", e));
  + .serve(make_service_fn(|_| {
  + async {
  + Ok::<_, hyper::Error>(service_fn(index2))
  + }
  + }));
  println!("Listening on http://{} and http://{}", addr1, addr2);
  - rt::spawn(srv1);
  - rt::spawn(srv2);
  + let _ret = join(srv1, srv2).await;
  Ok(())
  - }));
  }
  