Context propagation from client to server

context_propagation.go

unc runTestServer() string {
	slowServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		incoming, _ := httputil.DumpRequest(r, false)
		fmt.Printf("Server: Incoming Request %s", string(incoming))
		ctx := r.Context()
		echan := make(chan error)
		go func() {
			time.Sleep(12 * time.Second) // Do difficult Job
			_, err := w.Write([]byte("Hello There!"))
			echan <- err

		}()
		select {
		case <-ctx.Done():
			fmt.Printf("Error %s", ctx.Err().Error())
		case err := <-echan:
			if err != nil {
				w.WriteHeader(500)
			}
		}

	}))
	return slowServer.URL
}