Add dedicated tracing/logging example (#155)

Useful to link to since several have asked.

examples/README.md

@@ -18,7 +18,7 @@
 - [`chat`](../examples/chat.rs) - Chat application example.
 - [`404`](../examples/404.rs) - Custom 404 page.
 - [`async-graphql`](../examples/async-graphql) - GraphQL example using [`async-graphql`](https://crates.io/crates/async-graphql).
-
+- [`tracing_aka_logging`](../examples/tracing_aka_logging) - How to setup and configure tracing/logging.
 
 # Community showcase
 

examples/tracing_aka_logging.rs

@@ -0,0 +1,37 @@
+//! Run with
+//!
+//! ```not_rust
+//! cargo run --example tracing_aka_logging
+//! ```
+
+use axum::prelude::*;
+use std::net::SocketAddr;
+use tower_http::trace::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", "tracing_aka_logging=debug,tower_http=debug")
+    }
+    tracing_subscriber::fmt::init();
+
+    // build our application with a route
+    let app = route("/", get(handler))
+        // `TraceLayer` is provided by tower-http so you have to add that as a dependency.
+        // It provides good defaults but is also very customizable.
+        // See https://docs.rs/tower-http/0.1.1/tower_http/trace/index.html for more details.
+        .layer(TraceLayer::new_for_http());
+
+    // run it
+    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 handler() -> response::Html<&'static str> {
+    response::Html("<h1>Hello, World!</h1>")
+}