message: docs(server): doc test to async/await
diff: //! ## Example
  //!
  //! ```no_run
  -//! extern crate hyper;
  -//!
  -//! use hyper::{Body, Response, Server};
  -//! use hyper::service::service_fn_ok;
  +//! # #![feature(async_await)]
  +//! use hyper::{Body, Error, Response, Server};
  +//! use hyper::service::{make_service_fn, service_fn};
  //!
  //! # #[cfg(feature = "runtime")]
  -//! fn main() {
  -//! # use hyper::rt::Future;
  +//! # #[hyper::rt::main]
  +//! async fn main() {
  //! // Construct our SocketAddr to listen on...
  //! let addr = ([127, 0, 0, 1], 3000).into();
  //!
  //! // And a MakeService to handle each connection...
  -//! let make_service = || {
  -//! service_fn_ok(|_req| {
  -//! Response::new(Body::from("Hello World"))
  -//! })
  -//! };
  +//! let make_service = make_service_fn(|_| async {
  +//! Ok::<_, Error>(service_fn(|_req| async {
  +//! Ok::<_, Error>(Response::new(Body::from("Hello World")))
  +//! }))
  +//! });
  //!
  //! // Then bind and serve...
  //! let server = Server::bind(&addr)
  //! .serve(make_service);
  //!
  //! // Finally, spawn `server` onto an Executor...
  -//! hyper::rt::run(server.map_err(|e| {
  +//! if let Err(e) = server.await {
  //! eprintln!("server error: {}", e);
  -//! }));
  +//! }
  //! }
  //! # #[cfg(not(feature = "runtime"))]
  //! # fn main() {}
  