func ExampleNewTLSServer() {
	ts := httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintln(w, "Hello, client")
	}))
	defer ts.Close()

	cert, err := x509.ParseCertificate(ts.TLS.Certificates[0].Certificate[0])
	if err != nil {
		log.Fatal(err)
	}

	certpool := x509.NewCertPool()
	certpool.AddCert(cert)

	client := http.Client{
		Transport: &http.Transport{
			TLSClientConfig: &tls.Config{
				RootCAs: certpool,
			},
		},
	}

	res, err := client.Get(ts.URL)
	if err != nil {
		log.Fatal(err)
	}
	defer res.Body.Close()

	greeting, err := ioutil.ReadAll(res.Body)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("%s", greeting)
	// Output: Hello, client
}