A mock one time token

onetime_token_server.go

package main

import (
	"fmt"
	"log"
	"math/rand"
	"net/http"
	"time"
)

func init() {
	rand.Seed(time.Now().UnixNano())
}

var letterRunes = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")

func RandStringRunes(n int) string {
	b := make([]rune, n)
	for i := range b {
		b[i] = letterRunes[rand.Intn(len(letterRunes))]
	}
	return string(b)
}

var issuedTokens = make(map[string]int)

// returns an http.HandlerFunc that processes http requests to ...
func HandleIssueToken(w http.ResponseWriter, r *http.Request) {
	token := RandStringRunes(10)
	issuedTokens[token] = 0
	w.Write([]byte(token))
}

// HandleSample writes a hello message to response.
func HandleAuthorized(w http.ResponseWriter, r *http.Request) {
	tok := r.Header.Get("Authorization")
	if tok == "" {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	used, ok := issuedTokens[tok]
	if !ok {
		w.WriteHeader(http.StatusUnauthorized)
		w.Write([]byte("Unauthorized, please issuee a new token"))
		return
	}

	if used > 1 {
		w.WriteHeader(401)
		w.Write([]byte("Token is expired"))
		return
	}

	// dump issused token
	for k, v := range issuedTokens {
		fmt.Println(k, v)
	}
	issuedTokens[tok]++
	w.Write([]byte("Welcome, you can see this resource"))
}

func main() {
	addr := ":1234"
	r := http.NewServeMux()
	r.HandleFunc("/admin", HandleAuthorized)
	r.HandleFunc("/token", HandleIssueToken)
	svr := &http.Server{
		Addr:    addr,
		Handler: r,
	}
	log.Println("server started", addr)
	log.Fatal(svr.ListenAndServe())
}