app: Implement graceful shutdown

When calling `axum::serve`, use `.with_graceful_shutdown()` to register
a `ctrl+c` handler, so that Iocaine can be gracefully shut down. This
also allows gracefully shutting it down when running inside a container.

Fixes #1, thanks @alciregi!

Signed-off-by: Gergely Nagy <me@gergo.csillger.hu>

src/iocaine/app.rs

@@ -52,7 +52,29 @@ impl Iocaine {
             .layer(Extension(self.clone()))
             .layer(tower_http::trace::TraceLayer::new_for_http());
         let listener = tokio::net::TcpListener::bind(bind).await?;
-        axum::serve(listener, app).await
+        axum::serve(listener, app)
+            .with_graceful_shutdown(shutdown_signal())
+            .await
+    }
+}
+
+async fn shutdown_signal() {
+    let ctrl_c = async {
+        tokio::signal::ctrl_c()
+            .await
+            .expect("failed to install Ctrl+C handler");
+    };
+
+    let terminate = async {
+        tokio::signal::unix::signal(tokio::signal::unix::SignalKind::terminate())
+            .expect("failed to install signal handler")
+            .recv()
+            .await;
+    };
+
+    tokio::select! {
+        _ = ctrl_c => {},
+        _ = terminate => {},
     }
 }