Cancel database query with context

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A simple example on how cancel a query with context.

An short example of how we can use the context package to cancel an query request. We are gonna use the WithTimeout function to do this.

First a simple webserver:

func main() {
	port := ":8000"

	// query route
	http.HandleFunc("/query", query)

	log.Println("Listening on " + port)
	log.Fatal(http.ListenAndServe(port, nil))
}

The database handler:

func query(w http.ResponseWriter, r *http.Request) {
	// We create a new context with an given timeout at 1 second
	ctx, cancel := context.WithTimeout(r.Context(), time.Second*1)

	defer cancel()

	// simulating an database query
	time.Sleep(time.Second * 2)

	// If the timeout is exceeded ctx.Done() will be triggered
	select {
	case <-ctx.Done():
		w.Write([]byte(ctx.Err()))
	default:
		w.Write([]byte(`timeout not exceeded`))
	}
}

Thanks for reading