Timeout requests with a context

// httpbin.org is a service for testing HTTP client
// this URL waits 3 seconds before returning a response
uri := "https://httpbin.org/delay/3"
req, err := http.NewRequest("GET", uri, nil)
if err != nil {
	log.Fatalf("http.NewRequest() failed with '%s'\n", err)
}

// create a context indicating 100 ms timeout
ctx, _ := context.WithTimeout(context.Background(), time.Millisecond*100)
// get a new request based on original request but with the context
req = req.WithContext(ctx)

resp, err := http.DefaultClient.Do(req)
if err != nil {
	// the request should timeout because we want to wait max 100 ms
	// but the server doesn't return response for 3 seconds
	log.Fatalf("http.DefaultClient.Do() failed with:\n'%s'\n", err)
}
defer resp.Body.Close()