Add README

README.md

@@ -1,7 +1,123 @@
 # gauth-go
 
+---
+
 [![Go Reference](https://pkg.go.dev/badge/github.com/onee-only/gauth-go.svg)](https://pkg.go.dev/github.com/onee-only/gauth-go)
 [![codecov](https://codecov.io/gh/onee-only/gauth-go/graph/badge.svg?token=CG5WOHFTMX)](https://codecov.io/gh/onee-only/gauth-go)
 [![Go Report Card](https://goreportcard.com/badge/github.com/onee-only/gauth-go)](https://goreportcard.com/report/github.com/onee-only/gauth-go)
 
 Package gauth is go version of gauth sdk.
+
+## Description
+
+---
+
+광주소프트웨어 마이스터고등학교의 통합 계정 관리 서비스인 ```GAuth```를 ```Golang```으로 더 손쉽게 사용할 수 있도록 만들어진 라이브러리 입니다
+
+## Installation
+
+```
+go get -u https://github.com/onee-only/gauth-go
+```
+
+## How To Use
+
+### Client Initialization 
+```go
+package main
+
+import(
+	"github.com/onee-only/gauth-go"
+)
+
+func main() {
+	client := gauth.NewDefaultClient(gauth.ClientOpts{
+		ClientID:     "clientID",
+		ClientSecret: "clientSecret",
+		RedirectURI:  "localhost:8080",
+	})
+}
+```
+
+### code 발급
+```go
+package main
+
+import (
+	"log"
+
+	"github.com/onee-only/gauth-go"
+)
+
+func issueCode(client *gauth.Client) {
+	code, err := client.IssueCode("email", "password")
+	if err != nil {
+		// You shouldn't use panic in your code.
+		panic(err)
+	}
+	log.Println(code)
+}
+```
+
+### Token 발급
+
+```go
+package main
+
+import (
+	"log"
+
+	"github.com/onee-only/gauth-go"
+)
+
+func issueToken(client *gauth.Client) {
+	accessToken, refreshToken, err := client.IssueToken("code")
+	if err != nil {
+		// You shouldn't use panic in your code.
+		panic(err)
+	}
+	log.Println(accessToken)
+	log.Println(refreshToken)
+}
+```
+
+### Token 재발급
+```go
+package main
+
+import (
+	"log"
+
+	"github.com/onee-only/gauth-go"
+)
+
+func reIssueToken(client *gauth.Client) {
+	access, refresh, err := client.ReIssueToken("refreshToken")
+	if err != nil {
+		// You shouldn't use panic in your code.
+		panic(err)
+	}
+	log.Println(access)
+	log.Println(refresh)
+}
+```
+
+### 유저 정보 가져오기
+```go
+package main
+
+import (
+	"log"
+
+	"github.com/onee-only/gauth-go"
+)
+
+func getUserInfo(client *gauth.Client) {
+	info, err := client.GetUserInfo("accessToken")
+	if err != nil {
+		// You shouldn't use panic in your code.
+		panic(err)
+	}
+	log.Println(info)
+}
+```