fix: add tracing calls to tracing-aka-logging example closures (#3722)

examples/tracing-aka-logging/src/main.rs

@@ -65,21 +65,22 @@ async fn main() {
                     // You can use `_span.record("some_other_field", value)` in one of these
                     // closures to attach a value to the initially empty field in the info_span
                     // created above.
+                    tracing::debug!("started processing request")
                 })
                 .on_response(|_response: &Response, _latency: Duration, _span: &Span| {
-                    // ...
+                    tracing::debug!("finished processing request")
                 })
                 .on_body_chunk(|_chunk: &Bytes, _latency: Duration, _span: &Span| {
-                    // ...
+                    tracing::debug!("sending body chunk")
                 })
                 .on_eos(
                     |_trailers: Option<&HeaderMap>, _stream_duration: Duration, _span: &Span| {
-                        // ...
+                        tracing::debug!("stream closed")
                     },
                 )
                 .on_failure(
                     |_error: ServerErrorsFailureClass, _latency: Duration, _span: &Span| {
-                        // ...
+                        tracing::error!("something went wrong")
                     },
                 ),
         );