Simplify graceful shutdown (#673)

examples/graceful-shutdown/src/main.rs

@@ -0,0 +1,55 @@
+//! Run with
+//!
+//! ```not_rust
+//! cargo run -p example-graceful-shutdown
+//! kill or ctrl-c
+//! ```
+
+use axum::{response::Html, routing::get, Router};
+use std::net::SocketAddr;
+use tokio::signal;
+
+#[tokio::main]
+async fn main() {
+    // build our application with a route
+    let app = Router::new().route("/", get(handler));
+
+    // run it
+    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
+    println!("listening on {}", addr);
+    axum::Server::bind(&addr)
+        .serve(app.into_make_service())
+        .with_graceful_shutdown(shutdown_signal())
+        .await
+        .unwrap();
+}
+
+async fn handler() -> Html<&'static str> {
+    Html("<h1>Hello, World!</h1>")
+}
+
+async fn shutdown_signal() {
+    let ctrl_c = async {
+        signal::ctrl_c()
+            .await
+            .expect("failed to install Ctrl+C handler");
+    };
+
+    #[cfg(unix)]
+    let terminate = async {
+        signal::unix::signal(signal::unix::SignalKind::terminate())
+            .expect("failed to install signal handler")
+            .recv()
+            .await;
+    };
+
+    #[cfg(not(unix))]
+    let terminate = std::future::pending::<()>();
+
+    tokio::select! {
+        _ = ctrl_c => {},
+        _ = terminate => {},
+    }
+
+    println!("signal received, starting graceful shutdown");
+}