message: docs(service): `service_fn` doc test to async/await
diff: @@ -43,10 +43,11 @@ pub trait Service {
  /// # Example
  ///
  /// ```rust
  +/// # #![feature(async_await)]
  /// use hyper::{Body, Request, Response, Version};
  /// use hyper::service::service_fn;
  ///
  -/// let service = service_fn(|req: Request<Body>| {
  +/// let service = service_fn(|req: Request<Body>| async move{
  /// if req.version() == Version::HTTP_11 {
  /// Ok(Response::new(Body::from("Hello World")))
  /// } else {
  