Async/await polish (#1058)

A general refresh of Tokio's experimental async / await support.

async-await/src/echo_server.rs

@@ -0,0 +1,42 @@
+#![feature(await_macro, async_await)]
+
+use tokio::await;
+use tokio::net::{TcpListener, TcpStream};
+use tokio::prelude::*;
+
+use std::net::SocketAddr;
+
+fn handle(mut stream: TcpStream) {
+    tokio::spawn_async(async move {
+        let mut buf = [0; 1024];
+
+        loop {
+            match await!(stream.read_async(&mut buf)).unwrap() {
+                0 => break, // Socket closed
+                n => {
+                    // Send the data back
+                    await!(stream.write_all_async(&buf[0..n])).unwrap();
+                }
+            }
+        }
+    });
+}
+
+#[tokio::main]
+async fn main() {
+    use std::env;
+
+    let addr = env::args().nth(1).unwrap_or("127.0.0.1:8080".to_string());
+    let addr = addr.parse::<SocketAddr>().unwrap();
+
+    // Bind the TCP listener
+    let listener = TcpListener::bind(&addr).unwrap();
+    println!("Listening on: {}", addr);
+
+    let mut incoming = listener.incoming();
+
+    while let Some(stream) = await!(incoming.next()) {
+        let stream = stream.unwrap();
+        handle(stream);
+    }
+}