Remove bot method StopReceivingUpdates()

The StopReceivingUpdates() was used to stop a goroutine created at
GetUpdatesChannel().

If StopReceivingUpdates() were called twice or if GetUpdatesChannel()
were called after a StopReceivingUpdates() the bot behavior would be
incorrect due to 'shutdownChannel' close.

This commit removes StopReceivingUpdates() and modifies UpdatesChannel
struct to have a Shutdown() method which can stop both the associated
goroutine and http handler to feed the updates channel.

Signed-off-by: Vinicius Tinti <viniciustinti@gmail.com>

bot.go

@@ -24,9 +24,8 @@ type BotAPI struct {
 	Debug  bool   `json:"debug"`
 	Buffer int    `json:"buffer"`
 
-	Self            User         `json:"-"`
-	Client          *http.Client `json:"-"`
-	shutdownChannel chan interface{}
+	Self   User         `json:"-"`
+	Client *http.Client `json:"-"`
 }
 
 // NewBotAPI creates a new BotAPI instance.
@@ -42,10 +41,9 @@ func NewBotAPI(token string) (*BotAPI, error) {
 // It requires a token, provided by @BotFather on Telegram.
 func NewBotAPIWithClient(token string, client *http.Client) (*BotAPI, error) {
 	bot := &BotAPI{
-		Token:           token,
-		Client:          client,
-		Buffer:          100,
-		shutdownChannel: make(chan interface{}),
+		Token:  token,
+		Client: client,
+		Buffer: 100,
 	}
 
 	self, err := bot.GetMe()
@@ -380,11 +378,12 @@ func (bot *BotAPI) GetWebhookInfo() (WebhookInfo, error) {
 // GetUpdatesChan starts and returns a channel for getting updates.
 func (bot *BotAPI) GetUpdatesChan(config UpdateConfig) UpdatesChannel {
 	ch := make(chan Update, bot.Buffer)
+	done := make(chan struct{})
 
 	go func() {
 		for {
 			select {
-			case <-bot.shutdownChannel:
+			case <-done:
 				return
 			default:
 			}
@@ -401,28 +400,37 @@ func (bot *BotAPI) GetUpdatesChan(config UpdateConfig) UpdatesChannel {
 			for _, update := range updates {
 				if update.UpdateID >= config.Offset {
 					config.Offset = update.UpdateID + 1
-					ch <- update
+
+					select {
+					case ch <- update:
+					case <-done:
+						return
+					}
 				}
 			}
 		}
 	}()
 
-	return ch
-}
-
-// StopReceivingUpdates stops the go routine which receives updates
-func (bot *BotAPI) StopReceivingUpdates() {
-	if bot.Debug {
-		log.Println("Stopping the update receiver routine...")
+	updatesCh := UpdatesChannel{
+		channel: ch,
+		done:    done,
 	}
-	close(bot.shutdownChannel)
+
+	return updatesCh
 }
 
 // ListenForWebhook registers a http handler for a webhook.
 func (bot *BotAPI) ListenForWebhook(pattern string) UpdatesChannel {
 	ch := make(chan Update, bot.Buffer)
+	done := make(chan struct{})
 
 	http.HandleFunc(pattern, func(w http.ResponseWriter, r *http.Request) {
+		select {
+		case <-done:
+			return
+		default:
+		}
+
 		bytes, _ := ioutil.ReadAll(r.Body)
 
 		var update Update
@@ -431,7 +439,12 @@ func (bot *BotAPI) ListenForWebhook(pattern string) UpdatesChannel {
 		ch <- update
 	})
 
-	return ch
+	updatesCh := UpdatesChannel{
+		channel: ch,
+		done:    done,
+	}
+
+	return updatesCh
 }
 
 // GetChat gets information about a chat.

bot_test.go

@@ -543,7 +543,7 @@ func ExampleNewBotAPI() {
 	time.Sleep(time.Millisecond * 500)
 	updates.Clear()
 
-	for update := range updates {
+	for update := range updates.Channel() {
 		if update.Message == nil {
 			continue
 		}
@@ -585,7 +585,7 @@ func ExampleNewWebhook() {
 	updates := bot.ListenForWebhook("/" + bot.Token)
 	go http.ListenAndServeTLS("0.0.0.0:8443", "cert.pem", "key.pem", nil)
 
-	for update := range updates {
+	for update := range updates.Channel() {
 		log.Printf("%+v\n", update)
 	}
 }
@@ -603,7 +603,7 @@ func ExampleInlineConfig() {
 
 	updates := bot.GetUpdatesChan(u)
 
-	for update := range updates {
+	for update := range updates.Channel() {
 		if update.InlineQuery == nil { // if no inline query, ignore it
 			continue
 		}

types.go

@@ -39,13 +39,28 @@ type Update struct {
 	PreCheckoutQuery   *PreCheckoutQuery   `json:"pre_checkout_query"`
 }
 
-// UpdatesChannel is the channel for getting updates.
-type UpdatesChannel <-chan Update
+// UpdatesChannel is the struct that holds a channel for getting updates.
+type UpdatesChannel struct {
+	channel chan Update
+	done    chan struct{}
+}
+
+// Return Update channel
+func (updatesCh UpdatesChannel) Channel() <-chan Update {
+	return updatesCh.channel
+}
+
+// Stop channel feeding by goroutine or http handlers.
+//
+// It may not feed the update channel with all fetched/received Updates.
+func (updatesCh UpdatesChannel) Shutdown() {
+	updatesCh.done <- struct{}{}
+}
 
 // Clear discards all unprocessed incoming updates.
-func (ch UpdatesChannel) Clear() {
-	for len(ch) != 0 {
-		<-ch
+func (updatesCh UpdatesChannel) Clear() {
+	for len(updatesCh.channel) != 0 {
+		<-updatesCh.channel
 	}
 }