Golang OAuth 2.0 Server

     +--------+                               +---------------+
     |        |--(A)- Authorization Request ->|   Resource    |
     |        |                               |     Owner     |
     |        |<-(B)-- Authorization Grant ---|               |
     |        |                               +---------------+
     |        |
     |        |                               +---------------+
     |        |--(C)-- Authorization Grant -->| Authorization |
     | Client |                               |     Server    |
     |        |<-(D)----- Access Token -------|               |
     |        |                               +---------------+
     |        |
     |        |                               +---------------+
     |        |--(E)----- Access Token ------>|    Resource   |
     |        |                               |     Server    |
     |        |<-(F)--- Protected Resource ---|               |
     +--------+                               +---------------+

go get -u -v github.com/go-oauth2/oauth2/v4/...

package main

import (
	"log"
	"net/http"

	"github.com/go-oauth2/oauth2/v4/errors"
	"github.com/go-oauth2/oauth2/v4/manage"
	"github.com/go-oauth2/oauth2/v4/models"
	"github.com/go-oauth2/oauth2/v4/server"
	"github.com/go-oauth2/oauth2/v4/store"
)

func main() {
	manager := manage.NewDefaultManager()
	// token memory store
	manager.MustTokenStorage(store.NewMemoryTokenStore())

	// client memory store
	clientStore := store.NewClientStore()
	clientStore.Set("000000", &models.Client{
		ID:     "000000",
		Secret: "999999",
		Domain: "http://localhost",
	})
	manager.MapClientStorage(clientStore)

	srv := server.NewDefaultServer(manager)
	srv.SetAllowGetAccessRequest(true)
	srv.SetClientInfoHandler(server.ClientFormHandler)

	srv.SetInternalErrorHandler(func(err error) (re *errors.Response) {
		log.Println("Internal Error:", err.Error())
		return
	})

	srv.SetResponseErrorHandler(func(re *errors.Response) {
		log.Println("Response Error:", re.Error.Error())
	})

	http.HandleFunc("/authorize", func(w http.ResponseWriter, r *http.Request) {
		err := srv.HandleAuthorizeRequest(w, r)
		if err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
		}
	})

	http.HandleFunc("/token", func(w http.ResponseWriter, r *http.Request) {
		srv.HandleTokenRequest(w, r)
	})

	log.Fatal(http.ListenAndServe(":9096", nil))
}

go build server.go

./server

{
  "access_token": "J86XVRYSNFCFI233KXDL0Q",
  "expires_in": 7200,
  "scope": "read",
  "token_type": "Bearer"
}

import (
	"github.com/go-oauth2/oauth2/v4/generates"
	"github.com/dgrijalva/jwt-go"
)

// ...
manager.MapAccessGenerate(generates.NewJWTAccessGenerate("", []byte("00000000"), jwt.SigningMethodHS512))

// Parse and verify jwt access token
token, err := jwt.ParseWithClaims(access, &generates.JWTAccessClaims{}, func(t *jwt.Token) (interface{}, error) {
	if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
		return nil, fmt.Errorf("parse error")
	}
	return []byte("00000000"), nil
})
if err != nil {
	// panic(err)
}

claims, ok := token.Claims.(*generates.JWTAccessClaims)
if !ok || !token.Valid {
	// panic("invalid token")
}