An HTTP client for go-server-timing middleware.

• An HTTP Client or RoundTripper, fully compatible with Go's standard library.
• Automatically time HTTP requests sent from an HTTP handler.
• Collects all timing headers from upstream servers.
• Customize timing headers according to the request, response and error of the HTTP round trip.

go get -u github.com/posener/client-timing

1. Add a *clienttiming.Timer to your server handler, or create it in the handler function itself.

2. Wrap the http.Handler with servertiming.Middleware.

3. In the handler function, having timer of type *clienttiming.Timer and req is the *http.Request:

   a. Create an *http.Client using timer.Client(req.Context())

   b. Or create an http.RoundTripper using timer.Transport(req.Context())

4. Use option a or b directly or inject it to a library that accepts them, in your outgoing HTTP request from the handler.

5. That is it! the timing header will appear in the response from the handler.

Suppose we have an HTTP handler:

type handler struct {
	timer *clienttiming.Timer
}

Our usage of that handler will be:

func main() {
	h := &handler{
		timer: clienttiming.New(clienttiming.WithName("my-server")),
	}
	log.Fatal(http.ListenAndServe(":8080", servertiming.Middleware(h)))
}

func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	// Create an http client using the request context
	c := h.timer.Client(r.Context())

	// Perform HTTP requests, as many as you like
	resp, err := c.Get("https://golang.org/")

	...
}

func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	// Instrument an http client with a timing transport
	c := &http.Client{
		Transport: h.timer.Transport(r.Context()),
	}

	// Perform HTTP requests, as many as you like
	resp, err := c.Get("https://golang.org/")

	...
}

go run ./example/main.go