// Create a public/private key pair (ECDSA)
private, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
if err != nil {
	panic(err)
}

// Create a JWT token, sign it with the private key.
token, err := jwt.New(
	header.Parameters{
		header.Type:      jwt.Type,
		header.Algorithm: jwa.ES256,
	},
	jwt.ClaimsSet{
		"sub":  "1234567890",
		"name": "John Doe",
	},
	private,
)
if err != nil {
	panic(err)
}

mux := http.NewServeMux()

mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
	bearerToken, err := jwt.FromHTTPAuthorizationHeader(r)
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	token, err = jwt.ParseAndVerify(bearerToken, jwt.WithKey(&private.PublicKey))
	if err != nil {
		w.WriteHeader(http.StatusUnauthorized)
		return
	}

	sub, err := token.Claims.Get(jwt.Subject)
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	if sub != "1234567890" {
		w.WriteHeader(http.StatusUnauthorized)
		return
	}

	name, err := token.Claims.Get("name")
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	w.WriteHeader(http.StatusOK)
	w.Write([]byte(fmt.Sprintf("Welcome back, %s!", name)))
})

fmt.Println("Listening on http://127.0.0.1:8080")

fmt.Printf("Try running: curl http://127.0.0.1:8080 -H 'Authorization: Bearer %s' -v\n", token)

err = http.ListenAndServe("127.0.0.1:8080", mux)
if err != nil {
	panic(err)
}