Env documentation, log, last hope handler

Signed-off-by: Terekhin Alexandr <alex@bearns.me>

go.mod

@@ -1,3 +1,5 @@
 module bearns.me/didinst/tg-bot-example
 
 go 1.15
+
+require gopkg.in/tucnak/telebot.v2 v2.3.5

main.go

@@ -8,37 +8,42 @@ import (
 )
 
 func main() {
-    var (
-        port      = os.Getenv("PORT")
-        publicURL = os.Getenv("PUBLIC_URL")
-        token     = os.Getenv("TOKEN")
-        apiURL	= os.Getenv("API_URL")
-    )
-
-    webhook := &tb.Webhook{
-        Listen:   ":" + port,
-        Endpoint: &tb.WebhookEndpoint{PublicURL: publicURL},
-    }
-
-    pref := tb.Settings{
-        Token:  token,
-        Poller: webhook,
-        URL:	 apiURL,
-    }
-
-    b, err := tb.NewBot(pref)
-    if err != nil {
-        log.Fatal(err)
-    }	
+	var (
+		port      = os.Getenv("PORT")       // Bot app listening port, same as port in API_URL
+		publicURL = os.Getenv("PUBLIC_URL") // http://<telegram-api-server>:<port>
+		token     = os.Getenv("TOKEN")      // Token from @BotFather
+		apiURL    = os.Getenv("API_URL")    // http://<bot-app-host>:<bot-app-port>/<random-name-path>
+	)
+
+	webhook := &tb.Webhook{
+		Listen:   ":" + port,
+		Endpoint: &tb.WebhookEndpoint{PublicURL: publicURL},
+	}
+
+	pref := tb.Settings{
+		Token:  token,
+		Poller: webhook,
+		URL:    apiURL,
+	}
 
+	b, err := tb.NewBot(pref)
 	if err != nil {
 		log.Fatal(err)
-		return
 	}
 
 	b.Handle("/hello", func(m *tb.Message) {
-		b.Send(m.Sender, "Hello World!")
+		log.Print(m)
+		_, err := b.Send(m.Sender, "Hello World!")
+		if err != nil {
+			log.Print(err)
+		}
+	})
+
+	b.Handle(tb.OnText, func(m *tb.Message) {
+		log.Print(m)
+		// all the text messages that weren't
+		// captured by existing handlers
 	})
 
 	b.Start()
-}
+}