In example-service, print the port the server is listened on.

This is helpful when passing starting the server with --port 0.

example-service/src/server.rs

@@ -54,6 +54,7 @@ async fn main() -> anyhow::Result<()> {
     // JSON transport is provided by the json_transport tarpc module. It makes it easy
     // to start up a serde-powered json serialization strategy over TCP.
     let mut listener = tarpc::serde_transport::tcp::listen(&server_addr, Json::default).await?;
+    tracing::info!("Listening on port {}", listener.local_addr().port());
     listener.config_mut().max_frame_length(usize::MAX);
     listener
         // Ignore accept errors.