Fix bug with update channel closing, add ListenForWebhookRespReqFormat method, for using in serverless apps, add example to README.md, add exaple pf a published bot on AWS Lambda

Author: farit2000

README.md

@@ -110,6 +110,74 @@ func main() {
 }
 ```
 
+If you need to publish your bot on AWS Lambda(or something like it) and AWS API Gateway,
+you can use such example:
+
+In this code used AWS Lambda Go net/http server adapter [algnhsa](https://github.com/akrylysov/algnhsa)
+
+```go
+package main
+
+import (
+	"github.com/akrylysov/algnhsa"
+	"github.com/go-telegram-bot-api/telegram-bot-api"
+	"log"
+	"net/http"
+)
+
+func answer(w http.ResponseWriter, r *http.Request) {
+	bot, err := tgbotapi.NewBotAPI("MyAwesomeBotToken")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	bot.Debug = true
+	updates := bot.ListenForWebhookRespReqFormat(w, r)
+	for update := range updates {
+		if update.Message == nil {
+			continue
+		}
+		log.Printf("[%s] %s", update.Message.From.UserName, update.Message.Text)
+
+		msg := tgbotapi.NewMessage(update.Message.Chat.ID, update.Message.Text)
+		msg.ReplyToMessageID = update.Message.MessageID
+		_, err := bot.Send(msg)
+		if err != nil {
+			log.Printf("Error send message: %s | Error: %s", msg.Text, err.Error())
+		}
+	}
+}
+
+func setWebhook(_ http.ResponseWriter, _ *http.Request) {
+	bot, err := tgbotapi.NewBotAPI("MyAwesomeBotToken")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	bot.Debug = true
+
+	log.Printf("Authorized on account %s", bot.Self.UserName)
+
+	_, err = bot.SetWebhook(tgbotapi.NewWebhook("https://your_api_gateway_address.com/"+bot.Token))
+	if err != nil {
+		log.Fatal(err)
+	}
+	info, err := bot.GetWebhookInfo()
+	if err != nil {
+		log.Fatal(err)
+	}
+	if info.LastErrorDate != 0 {
+		log.Printf("Telegram callback failed: %s", info.LastErrorMessage)
+	}
+}
+
+func main() {
+	http.HandleFunc("/set_webhook", setWebhook)
+	http.HandleFunc("/MyAwesomeBotToken", answer)
+	algnhsa.ListenAndServe(http.DefaultServeMux, nil)
+}
+```
+
 If you need, you may generate a self signed certficate, as this requires
 HTTPS / TLS. The above example tells Telegram that this is your
 certificate and that it should be trusted, even though it is not

bot.go

@@ -567,11 +567,33 @@ func (bot *BotAPI) ListenForWebhook(pattern string) UpdatesChannel {
 		}
 
 		ch <- *update
+		close(ch)
 	})
 
 	return ch
 }
 
+// ListenForWebhookRespReqFormat registers a http handler for a webhook.
+func (bot *BotAPI) ListenForWebhookRespReqFormat(w http.ResponseWriter, r *http.Request) UpdatesChannel {
+	ch := make(chan Update, bot.Buffer)
+
+	func(w http.ResponseWriter, r *http.Request) {
+		update, err := bot.HandleUpdate(r)
+		if err != nil {
+			errMsg, _ := json.Marshal(map[string]string{"error": err.Error()})
+			w.WriteHeader(http.StatusBadRequest)
+			w.Header().Set("Content-Type", "application/json")
+			_, _ = w.Write(errMsg)
+			return
+		}
+
+		ch <- *update
+		close(ch)
+	}(w, r)
+
+	return ch
+}
+
 // HandleUpdate parses and returns update received via webhook
 func (bot *BotAPI) HandleUpdate(r *http.Request) (*Update, error) {
 	if r.Method != http.MethodPost {