fix(telegram): implement custom HTTP transport with TCP keepalive to prevent connection drops

pkg/channels/telegram.go

@@ -3,6 +3,7 @@ package channels
 import (
 	"context"
 	"fmt"
+	"net"
 	"net/http"
 	"net/url"
 	"os"
@@ -48,25 +49,31 @@ func NewTelegramChannel(cfg *config.Config, bus *bus.MessageBus) (*TelegramChann
 	var opts []telego.BotOption
 	telegramCfg := cfg.Channels.Telegram
 
+	// Always use a custom transport with TCP keepalive to prevent "unexpected EOF"
+	// errors caused by NAT/firewall silently dropping idle long-poll connections.
+	transport := &http.Transport{
+		DialContext: (&net.Dialer{
+			Timeout:   30 * time.Second,
+			KeepAlive: 30 * time.Second,
+		}).DialContext,
+		IdleConnTimeout:     90 * time.Second,
+		TLSHandshakeTimeout: 10 * time.Second,
+	}
+
 	if telegramCfg.Proxy != "" {
 		proxyURL, parseErr := url.Parse(telegramCfg.Proxy)
 		if parseErr != nil {
 			return nil, fmt.Errorf("invalid proxy URL %q: %w", telegramCfg.Proxy, parseErr)
 		}
-		opts = append(opts, telego.WithHTTPClient(&http.Client{
-			Transport: &http.Transport{
-				Proxy: http.ProxyURL(proxyURL),
-			},
-		}))
+		transport.Proxy = http.ProxyURL(proxyURL)
 	} else if os.Getenv("HTTP_PROXY") != "" || os.Getenv("HTTPS_PROXY") != "" {
-		// Use environment proxy if configured
-		opts = append(opts, telego.WithHTTPClient(&http.Client{
-			Transport: &http.Transport{
-				Proxy: http.ProxyFromEnvironment,
-			},
-		}))
+		transport.Proxy = http.ProxyFromEnvironment
 	}
 
+	opts = append(opts, telego.WithHTTPClient(&http.Client{
+		Transport: transport,
+	}))
+
 	bot, err := telego.NewBot(telegramCfg.Token, opts...)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create telegram bot: %w", err)