superfluous response.WriteHeader call still happens

[Zurvarian]

Description

As per release of https://github.com/open-telemetry/opentelemetry-go-contrib/releases/tag/v1.30.0
otelmux v0.55.0 has a fix to avoid superfluous calls to response.WriteHeader

However, even when using that version I still can see logs saying: http: superfluous response.WriteHeader call

And the log points towards: go.opentelemetry.io/contrib/instrumentation/github.com/gorilla/mux/otelmux.getRRW.func2.1
The code as seen in the library is as following.

func getRRW(writer http.ResponseWriter) *recordingResponseWriter {
	rrw := rrwPool.Get().(*recordingResponseWriter)
	rrw.written = false
	rrw.status = http.StatusOK
	rrw.writer = httpsnoop.Wrap(writer, httpsnoop.Hooks{
		Write: func(next httpsnoop.WriteFunc) httpsnoop.WriteFunc {
			return func(b []byte) (int, error) {
				if !rrw.written {
					rrw.written = true
				}
				return next(b)
			}
		},
		WriteHeader: func(next httpsnoop.WriteHeaderFunc) httpsnoop.WriteHeaderFunc {
			return func(statusCode int) {
				if !rrw.written {
					rrw.written = true
					rrw.status = statusCode
				}
				next(statusCode)
			}
		},
	})
	return rrw
}

In the above code there is a call to rrw.status = statusCode that is not protected with any semaphore, what makes me think this code can be invoked in a non thread-safe way, causing the log issue.
I'm not expert in OTEL code, so I can be wrong, though, simply it looks like the most obvious candidate.

Environment

• OS: linux
• Architecture: amd64
• Go Version: 1.23
• otelmux version: v0.55.0

Steps To Reproduce

1. Using this code the otelmux in a HTTP Server
2. Run any test endpoint
3. See error when pushing the metrics into the collector.

Expected behavior

I expect no logs to be shown due to superfluous calls to response.WriteHeader.

[dmathieu]

cc @akats7 as code owner.