dtan4/index.tmpl

## index.tmpl
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>weboauth</title>
  </head>
  <body>
    <h1>weboauth</h1>

    {{ if .logged_in }}
    Logged in: {{ .login }} ({{ .name }})
    {{ else }}
    <a href="/signin">Sign in with GitHub</a>
    {{ end }}
  </body>
</html>

## main.go
package main

import (
	"crypto/rand"
	"encoding/base64"
	"fmt"
	"io"
	"net/http"
	"os"
	"strings"

	"github.com/gin-gonic/contrib/sessions"
	"github.com/gin-gonic/gin"
	"github.com/google/go-github/github"
	"golang.org/x/oauth2"
	githuboauth "golang.org/x/oauth2/github"
)

func generateSecretKey() (string, error) {
	b := make([]byte, 32)
	_, err := io.ReadFull(rand.Reader, b)

	if err != nil {
		fmt.Println("error:", err)
		return "", err
	}

	return strings.TrimRight(base64.StdEncoding.EncodeToString(b), "="), nil
}

func main() {
	oauthConf := &oauth2.Config{
		ClientID:     os.Getenv("GITHUB_CLIENT_ID"),
		ClientSecret: os.Getenv("GITHUB_CLIENT_SECRET"),
		Scopes:       []string{"user"},
		Endpoint:     githuboauth.Endpoint,
	}

	secretKey := os.Getenv("SECRET_KEY_BASE")

	if secretKey == "" {
		sk, err := generateSecretKey()

		if err != nil {
			fmt.Fprintln(os.Stderr, err)
			os.Exit(1)
		}

		secretKey = sk
	}

	r := gin.Default()

	store := sessions.NewCookieStore([]byte(secretKey))
	r.Use(sessions.Sessions("paus", store))

	r.LoadHTMLGlob("templates/*")

	r.GET("/", func(c *gin.Context) {
		session := sessions.Default(c)
		token := session.Get("token")

		if token == nil {
			c.HTML(http.StatusOK, "index.tmpl", gin.H{
				"logged_in": false,
			})
		} else {
			oauthClient := oauthConf.Client(oauth2.NoContext, &oauth2.Token{AccessToken: token.(string)})
			client := github.NewClient(oauthClient)

			user, _, err := client.Users.Get("")

			if err != nil {
				c.String(http.StatusNotFound, "User not found")
				return
			}

			c.HTML(http.StatusOK, "index.tmpl", gin.H{
				"logged_in": true,
				"login":     user.Login,
				"name":      user.Name,
			})
		}
	})

	r.GET("/signin", func(c *gin.Context) {
		url := oauthConf.AuthCodeURL("hoge", oauth2.AccessTypeOnline)
		c.Redirect(http.StatusMovedPermanently, url)
	})

	r.GET("/callback", func(c *gin.Context) {
		code := c.Query("code")

		token, err := oauthConf.Exchange(oauth2.NoContext, code)

		if err != nil {
			c.String(http.StatusBadRequest, "Error: %s", err)
			return
		}

		session := sessions.Default(c)
		fmt.Println(token.AccessToken)
		session.Set("token", token.AccessToken)
		session.Save()

		c.Redirect(http.StatusMovedPermanently, "/")
	})

	r.Run()
}
	<!DOCTYPE html>
	<html>
	<head>
	<meta charset="utf-8">
	<title>weboauth</title>
	</head>
	<body>
	<h1>weboauth</h1>

	{{ if .logged_in }}
	Logged in: {{ .login }} ({{ .name }})
	{{ else }}
	<a href="/signin">Sign in with GitHub</a>
	{{ end }}
	</body>
	</html>
	package main

	import (
	"crypto/rand"
	"encoding/base64"
	"fmt"
	"io"
	"net/http"
	"os"
	"strings"

	"github.com/gin-gonic/contrib/sessions"
	"github.com/gin-gonic/gin"
	"github.com/google/go-github/github"
	"golang.org/x/oauth2"
	githuboauth "golang.org/x/oauth2/github"
	)

	func generateSecretKey() (string, error) {
	b := make([]byte, 32)
	_, err := io.ReadFull(rand.Reader, b)

	if err != nil {
	fmt.Println("error:", err)
	return "", err
	}

	return strings.TrimRight(base64.StdEncoding.EncodeToString(b), "="), nil
	}

	func main() {
	oauthConf := &oauth2.Config{
	ClientID: os.Getenv("GITHUB_CLIENT_ID"),
	ClientSecret: os.Getenv("GITHUB_CLIENT_SECRET"),
	Scopes: []string{"user"},
	Endpoint: githuboauth.Endpoint,
	}

	secretKey := os.Getenv("SECRET_KEY_BASE")

	if secretKey == "" {
	sk, err := generateSecretKey()

	if err != nil {
	fmt.Fprintln(os.Stderr, err)
	os.Exit(1)
	}

	secretKey = sk
	}

	r := gin.Default()

	store := sessions.NewCookieStore([]byte(secretKey))
	r.Use(sessions.Sessions("paus", store))

	r.LoadHTMLGlob("templates/*")

	r.GET("/", func(c *gin.Context) {
	session := sessions.Default(c)
	token := session.Get("token")

	if token == nil {
	c.HTML(http.StatusOK, "index.tmpl", gin.H{
	"logged_in": false,
	})
	} else {
	oauthClient := oauthConf.Client(oauth2.NoContext, &oauth2.Token{AccessToken: token.(string)})
	client := github.NewClient(oauthClient)

	user, _, err := client.Users.Get("")

	if err != nil {
	c.String(http.StatusNotFound, "User not found")
	return
	}

	c.HTML(http.StatusOK, "index.tmpl", gin.H{
	"logged_in": true,
	"login": user.Login,
	"name": user.Name,
	})
	}
	})

	r.GET("/signin", func(c *gin.Context) {
	url := oauthConf.AuthCodeURL("hoge", oauth2.AccessTypeOnline)
	c.Redirect(http.StatusMovedPermanently, url)
	})

	r.GET("/callback", func(c *gin.Context) {
	code := c.Query("code")

	token, err := oauthConf.Exchange(oauth2.NoContext, code)

	if err != nil {
	c.String(http.StatusBadRequest, "Error: %s", err)
	return
	}

	session := sessions.Default(c)
	fmt.Println(token.AccessToken)
	session.Set("token", token.AccessToken)
	session.Save()

	c.Redirect(http.StatusMovedPermanently, "/")
	})

	r.Run()
	}