chore: Prepare to merge into actix-extras

tracing-actix-web/examples/request-id-response-header/src/main.rs

@@ -0,0 +1,41 @@
+use actix_web::{
+    dev::Service,
+    http::header::{HeaderName, HeaderValue},
+    web, App, HttpMessage, HttpServer,
+};
+use std::io;
+use tracing_actix_web::{RequestId, TracingLogger};
+
+async fn hello() -> &'static str {
+    "Hello world!"
+}
+
+#[actix_web::main]
+async fn main() -> io::Result<()> {
+    HttpServer::new(move || {
+        App::new()
+            // set the request id in the `x-request-id` response header
+            .wrap_fn(|req, srv| {
+                let request_id = req.extensions().get::<RequestId>().copied();
+                let res = srv.call(req);
+                async move {
+                    let mut res = res.await?;
+                    if let Some(request_id) = request_id {
+                        res.headers_mut().insert(
+                            HeaderName::from_static("x-request-id"),
+                            // this unwrap never fails, since UUIDs are valid ASCII strings
+                            HeaderValue::from_str(&request_id.to_string()).unwrap(),
+                        );
+                    }
+                    Ok(res)
+                }
+            })
+            .wrap(TracingLogger::default())
+            .service(web::resource("/hello").to(hello))
+    })
+    .bind("127.0.0.1:8080")?
+    .run()
+    .await?;
+
+    Ok(())
+}