Webhook on Kubernetes

main.go

package main
import (
    "context"
    "encoding/json"
    "log"
    "net/http"
    "github.com/google/go-github/github"
    "golang.org/x/oauth2"
    authentication "k8s.io/client-go/pkg/apis/authentication/v1beta1"
)
func main() {
    http.HandleFunc("/authenticate", func(w http.ResponseWriter, r *http.Request) {
        decoder := json.NewDecoder(r.Body)
        var tr authentication.TokenReview
        err := decoder.Decode(&tr)
        if err != nil {
            log.Println("[Error]", err.Error())
            w.WriteHeader(http.StatusBadRequest)
            json.NewEncoder(w).Encode(map[string]interface{}{
                "apiVersion": "authentication.k8s.io/v1beta1",
                "kind":       "TokenReview",
                "status": authentication.TokenReviewStatus{
                    Authenticated: false,
                },
            })
            return
        }
        // Check User
        ts := oauth2.StaticTokenSource(
            &oauth2.Token{AccessToken: tr.Spec.Token},
        )
        tc := oauth2.NewClient(oauth2.NoContext, ts)
        client := github.NewClient(tc)
        user, _, err := client.Users.Get(context.Background(), "")
        if err != nil {
            log.Println("[Error]", err.Error())
            w.WriteHeader(http.StatusUnauthorized)
            json.NewEncoder(w).Encode(map[string]interface{}{
                "apiVersion": "authentication.k8s.io/v1beta1",
                "kind":       "TokenReview",
                "status": authentication.TokenReviewStatus{
                    Authenticated: false,
                },
            })
            return
        }
        log.Printf("[Success] login as %s", *user.Login)
        w.WriteHeader(http.StatusOK)
        trs := authentication.TokenReviewStatus{
            Authenticated: true,
            User: authentication.UserInfo{
                Username: *user.Login,
                UID:      *user.Login,
            },
        }
        json.NewEncoder(w).Encode(map[string]interface{}{
            "apiVersion": "authentication.k8s.io/v1beta1",
            "kind":       "TokenReview",
            "status":     trs,
        })
    })
    log.Fatal(http.ListenAndServe(":3000", nil))
}