docs(examples): update single_threaded example to async/await

Author: weihanglo

examples/single_threaded.rs

@@ -0,0 +1,55 @@
+#![feature(async_await)]
+#![deny(warnings)]
+
+use std::cell::Cell;
+use std::rc::Rc;
+
+use hyper::{Body, Error, Response, Server};
+use hyper::service::{make_service_fn, service_fn};
+use tokio::runtime::current_thread;
+
+// Configure a runtime that runs everything on the current thread,
+// which means it can spawn !Send futures...
+#[hyper::rt::main(single_thread)]
+async fn main() {
+    pretty_env_logger::init();
+
+    let addr = ([127, 0, 0, 1], 3000).into();
+
+    // Using a !Send request counter is fine on 1 thread...
+    let counter = Rc::new(Cell::new(0));
+
+    let make_service = make_service_fn(move |_| {
+        // For each connection, clone the counter to use in our service...
+        let cnt = counter.clone();
+
+        async move {
+            Ok::<_, Error>(service_fn(move |_| {
+                let prev = cnt.get();
+                cnt.set(prev + 1);
+                let value = cnt.get();
+                async move {
+                    Ok::<_, Error>(Response::new(Body::from(
+                        format!("Request #{}", value)
+                    )))
+                }
+            }))
+        }
+    });
+
+    // Since the Server needs to spawn some background tasks, we needed
+    // to configure an Executor that can spawn !Send futures...
+    let exec = current_thread::TaskExecutor::current();
+
+    let server = Server::bind(&addr)
+        .executor(exec)
+        .serve(make_service);
+
+    println!("Listening on http://{}", addr);
+
+    // The server would block on current thread to await !Send futures.
+    if let Err(e) = server.await {
+        eprintln!("server error: {}", e);
+    }
+}
+