Goroutines通讯槽通道仅工作一次

Question

My first attempt to write code in Golang (1.12) with go-routine and channel communication. I have Telegram bot and piece of code which can communicate with bot when some update happened and answer needed. At the same time I try to put some web service which will get a message trough http GET and send it to Bot. And in fact it works, but only once. After it Bot part still working, but http Get request cannot be performed, it hang on till time out.

I try to use channel with buffer, but in this it stops working completely.

//App is a structure with Bot objects
type App struct {
    Router *mux.Router
    Bot
}

//Initialize is method to initialize App session
func (a *App) Initialize() {

    var err error

    a.Bot.BotAPI, err = telegram.NewBotAPI(TelegramBotAPIkey)
    checkErr(err)

    a.Router = mux.NewRouter()
    a.initializeRoutes()
    msgChanel = make(chan string)
}


func (a *App) initializeRoutes() {
    a.Router.HandleFunc("/", a.homePage).Methods("GET")
    a.Router.Path("/message/send").Queries("msg", "{msg}").HandlerFunc(a.getMessage).Methods("GET")
}


}

// Handling of requests to send/message
func (a *App) getMessage(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintln(w, "-----Send message to Bot-------")
    vars := mux.Vars(r)
    if vars["msg"] != "" {
        fmt.Fprintln(w, vars["msg"])
        msgChanel <- vars["msg"]
    }

// Run is all about running application
func (a *App) Run() {

    var wg sync.WaitGroup
    wg.Add(2)


    go func() {
        defer wg.Done()
        msg := <-msgChanel
        a.Bot.generateAnswer(msgid, msg)
    }()

    go func() {

        var msg string

        defer wg.Done()
        a.Bot.BotAPI.Debug = true

        u := telegram.NewUpdate(0)
        u.Timeout = 60

        updates, err := a.Bot.BotAPI.GetUpdatesChan(u)
        checkErr(err)

        for update := range updates {
            if update.Message == nil {
                continue
            }
            msg = ""
            msgid = update.Message.Chat.ID
            a.Bot.generateAnswer(msgid, msg)
        }
    }()

    log.Fatal(http.ListenAndServe(":8080", a.Router))

    wg.Wait()

}

My problem that there is no error message. I run application and then it is working in terms on Bot communication, but communication with web service happened only once. My first thought was that it is because of of channel blocking, but I send string to channel, then I read it, so it there are should not be any blocking. So my expectation is that each time when I send http GET with message text it will be immediately send to Bot, and system was ready to get next request.

Answer 1

Seems like 'msgChanel' is read only once with 'msg := <-msgChanel'. Channel is blocked and cannot be written into by the HTTP request handler. Maybe you should read channel values with a for loop.