add a jwt tutorial + go client

_examples/auth/jwt/tutorial/go-client/README.md

@@ -0,0 +1,12 @@
+# Go Client
+
+```sh
+$ go run .
+```
+
+```sh
+2020/11/04 21:08:40 Access Token:
+"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VyX2lkIjoiYTAwYzI3ZDEtYjVhYS00NjU0LWFmMTYtYjExNzNkZTY1NjI5Iiwicm9sZXMiOlsiYWRtaW4iXSwiaWF0IjoxNjA0NTE2OTIwLCJleHAiOjE2MDQ1MTc4MjAsImp0aSI6IjYzNmVmMDc0LTE2MzktNGJhZi1hNGNiLTQ4ZDM4NGMxMzliYSIsImlzcyI6Im15YXBwIn0.T9B0zG0AHShO5JfQgrMQBlToH33KHgp8nLMPFpN6QmM"
+2020/11/04 21:08:40 Todo Created:
+model.Todo{ID:"cfa38d7a-c556-4301-ae1f-fb90f705071c", UserID:"a00c27d1-b5aa-4654-af16-b1173de65629", Title:"test todo title", Body:"test todo body contents", CreatedAt:1604516920}
+```

_examples/auth/jwt/tutorial/go-client/client.go

@@ -0,0 +1,109 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+)
+
+// Client is the default http client instance used by the following methods.
+var Client = http.DefaultClient
+
+// RequestOption is a function which can be used to modify
+// a request instance before Do.
+type RequestOption func(*http.Request) error
+
+// WithAccessToken sets the given "token" to the authorization request header.
+func WithAccessToken(token []byte) RequestOption {
+	bearer := "Bearer " + string(token)
+	return func(req *http.Request) error {
+		req.Header.Add("Authorization", bearer)
+		return nil
+	}
+}
+
+// WithContentType sets the content-type request header.
+func WithContentType(cType string) RequestOption {
+	return func(req *http.Request) error {
+		req.Header.Set("Content-Type", cType)
+		return nil
+	}
+}
+
+// WithContentLength sets the content-length request header.
+func WithContentLength(length int) RequestOption {
+	return func(req *http.Request) error {
+		req.Header.Set("Content-Length", strconv.Itoa(length))
+		return nil
+	}
+}
+
+// Do fires a request to the server.
+func Do(method, url string, body io.Reader, opts ...RequestOption) (*http.Response, error) {
+	req, err := http.NewRequest(method, url, body)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, opt := range opts {
+		if err = opt(req); err != nil {
+			return nil, err
+		}
+	}
+
+	return Client.Do(req)
+}
+
+// JSON fires a request with "v" as client json data.
+func JSON(method, url string, v interface{}, opts ...RequestOption) (*http.Response, error) {
+	buf := new(bytes.Buffer)
+	err := json.NewEncoder(buf).Encode(v)
+	if err != nil {
+		return nil, err
+	}
+
+	opts = append(opts, WithContentType("application/json; charset=utf-8"))
+	return Do(method, url, buf, opts...)
+}
+
+// Form fires a request with "formData" as client form data.
+func Form(method, url string, formData url.Values, opts ...RequestOption) (*http.Response, error) {
+	encoded := formData.Encode()
+	body := strings.NewReader(encoded)
+
+	opts = append([]RequestOption{
+		WithContentType("application/x-www-form-urlencoded"),
+		WithContentLength(len(encoded)),
+	}, opts...)
+
+	return Do(method, url, body, opts...)
+}
+
+// BindResponse binds a response body to the "dest" pointer and closes the body.
+func BindResponse(resp *http.Response, dest interface{}) error {
+	contentType := resp.Header.Get("Content-Type")
+	if idx := strings.IndexRune(contentType, ';'); idx > 0 {
+		contentType = contentType[0:idx]
+	}
+
+	switch contentType {
+	case "application/json":
+		defer resp.Body.Close()
+		return json.NewDecoder(resp.Body).Decode(dest)
+	default:
+		return fmt.Errorf("unsupported content type: %s", contentType)
+	}
+}
+
+// RawResponse simply returns the raw response body.
+func RawResponse(resp *http.Response) ([]byte, error) {
+	defer resp.Body.Close()
+
+	return ioutil.ReadAll(resp.Body)
+}

_examples/auth/jwt/tutorial/go-client/main.go

@@ -0,0 +1,69 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+	"net/url"
+
+	"myapp/api"
+	"myapp/domain/model"
+)
+
+const base = "http://localhost:8080"
+
+func main() {
+	accessToken, err := authenticate("admin", "admin")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	log.Printf("Access Token:\n%q", accessToken)
+
+	todo, err := createTodo(accessToken, "test todo title", "test todo body contents")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	log.Printf("Todo Created:\n%#+v", todo)
+}
+
+func authenticate(username, password string) ([]byte, error) {
+	endpoint := base + "/signin"
+
+	data := make(url.Values)
+	data.Set("username", username)
+	data.Set("password", password)
+
+	resp, err := Form(http.MethodPost, endpoint, data)
+	if err != nil {
+		return nil, err
+	}
+
+	accessToken, err := RawResponse(resp)
+	return accessToken, err
+}
+
+func createTodo(accessToken []byte, title, body string) (model.Todo, error) {
+	var todo model.Todo
+
+	endpoint := base + "/todos"
+
+	req := api.TodoRequest{
+		Title: title,
+		Body:  body,
+	}
+
+	resp, err := JSON(http.MethodPost, endpoint, req, WithAccessToken(accessToken))
+	if err != nil {
+		return todo, err
+	}
+
+	if resp.StatusCode != http.StatusCreated {
+		rawData, _ := RawResponse(resp)
+		return todo, fmt.Errorf("failed to create a todo: %s", string(rawData))
+	}
+
+	err = BindResponse(resp, &todo)
+	return todo, err
+}