fix: cache chat_id after reading from file

Hey, good catch on the review! I added caching for the chat_id so we don't
read the file every single time. Now it checks if we've already got the
value cached and only reads from disk if we haven't seen it before.

- Added getChatID() method that returns cached value first
- Cache the chat_id in n.conf.ChatID after reading it from file
- Changed Notify() to call getChatID() instead of accessing ChatID directly

Signed-off-by: Andrew Leng <tennisleng@users.noreply.github.com>

Author: Andrew Leng

notify/telegram/telegram.go

@@ -138,17 +138,25 @@ func (n *Notifier) getBotToken() (string, error) {
 }
 
 func (n *Notifier) getChatID() (int64, error) {
+	// Return cached value if already set
+	if n.conf.ChatID != 0 {
+		return n.conf.ChatID, nil
+	}
+
+	// Read from file if ChatIDFile is configured
 	if len(n.conf.ChatIDFile) > 0 {
 		content, err := os.ReadFile(n.conf.ChatIDFile)
 		if err != nil {
 			return 0, fmt.Errorf("could not read %s: %w", n.conf.ChatIDFile, err)
 		}
-		chatIDStr := strings.TrimSpace(string(content))
-		chatID, err := strconv.ParseInt(chatIDStr, 10, 64)
+		chatID, err := strconv.ParseInt(strings.TrimSpace(string(content)), 10, 64)
 		if err != nil {
 			return 0, fmt.Errorf("could not parse chat_id from %s: %w", n.conf.ChatIDFile, err)
 		}
+		// Cache the value for future use
+		n.conf.ChatID = chatID
 		return chatID, nil
 	}
-	return n.conf.ChatID, nil
+
+	return 0, fmt.Errorf("chat_id not configured")
 }