Move all examples to their own crates (#201)

This makes it much clearer which dependencies each example has.

examples/websockets/src/main.rs

@@ -0,0 +1,95 @@
+//! Example websocket server.
+//!
+//! Run with
+//!
+//! ```not_rust
+//! cargo run -p example-websockets
+//! ```
+
+use axum::{
+    extract::{
+        ws::{Message, WebSocket, WebSocketUpgrade},
+        TypedHeader,
+    },
+    handler::get,
+    http::StatusCode,
+    response::IntoResponse,
+    routing::{nest, RoutingDsl},
+};
+use std::net::SocketAddr;
+use tower_http::{
+    services::ServeDir,
+    trace::{DefaultMakeSpan, TraceLayer},
+};
+
+#[tokio::main]
+async fn main() {
+    // Set the RUST_LOG, if it hasn't been explicitly defined
+    if std::env::var("RUST_LOG").is_err() {
+        std::env::set_var("RUST_LOG", "example_websockets=debug,tower_http=debug")
+    }
+    tracing_subscriber::fmt::init();
+
+    // build our application with some routes
+    let app = nest(
+        "/",
+        axum::service::get(
+            ServeDir::new("examples/websockets/assets").append_index_html_on_directories(true),
+        )
+        .handle_error(|error: std::io::Error| {
+            Ok::<_, std::convert::Infallible>((
+                StatusCode::INTERNAL_SERVER_ERROR,
+                format!("Unhandled internal error: {}", error),
+            ))
+        }),
+    )
+    // routes are matched from bottom to top, so we have to put `nest` at the
+    // top since it matches all routes
+    .route("/ws", get(ws_handler))
+    // logging so we can see whats going on
+    .layer(
+        TraceLayer::new_for_http().make_span_with(DefaultMakeSpan::default().include_headers(true)),
+    );
+
+    // run it with hyper
+    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
+    tracing::debug!("listening on {}", addr);
+    axum::Server::bind(&addr)
+        .serve(app.into_make_service())
+        .await
+        .unwrap();
+}
+
+async fn ws_handler(
+    ws: WebSocketUpgrade,
+    user_agent: Option<TypedHeader<headers::UserAgent>>,
+) -> impl IntoResponse {
+    if let Some(TypedHeader(user_agent)) = user_agent {
+        println!("`{}` connected", user_agent.as_str());
+    }
+
+    ws.on_upgrade(handle_socket)
+}
+
+async fn handle_socket(mut socket: WebSocket) {
+    if let Some(msg) = socket.recv().await {
+        if let Ok(msg) = msg {
+            println!("Client says: {:?}", msg);
+        } else {
+            println!("client disconnected");
+            return;
+        }
+    }
+
+    loop {
+        if socket
+            .send(Message::Text(String::from("Hi!")))
+            .await
+            .is_err()
+        {
+            println!("client disconnected");
+            return;
+        }
+        tokio::time::sleep(std::time::Duration::from_secs(3)).await;
+    }
+}