RoundTripper should work out of the box.

[nmiculinic]

In following example:

	client := &http.Client{Transport: &nethttp.Transport{}}
	req, err := http.NewRequest("GET", "http://google.com", nil)
	if err != nil {
		return err
	}
	req = req.WithContext(ctx) // extend existing trace, if any

	req, ht := nethttp.TraceRequest(tracer, req)
	defer ht.Finish()

	res, err := client.Do(req)
	if err != nil {
		return err
	}
	res.Body.Close()
	return nil

nethttp.TraceRequest is extra. It is ok for people wanting greater control, but it should default to using GlobalTracer().

Similar to opencensus variant, ochttp, https://github.com/census-instrumentation/opencensus-go/tree/master/plugin/ochttp, things work out of the box. Just using their server middleware and their roundtripper plus adding parent request headers to context (via req = req.WithContext(parent.Context()))

However currently without req, ht := nethttp.TraceRequest(tracer, req) parent span isn't correlated to the child span

[yurishkuro]

nethttp.TraceRequest is extra. It is ok for people wanting greater control, but it should default to using GlobalTracer().

I don't recall the full interactions here, but I think ideally everything should work with just this:

client := &http.Client{Transport: &nethttp.Transport{Tracer: tracer}}

And if instead the transport is created without a tracer, then the global one is used.