feat(go): init (from gotd example)

.env.example

@@ -1,5 +1,10 @@
-PHONE=+1234567890
-API_ID=123456789
-API_HASH=0123456789abcdef0123456789abcdef
+# TG_PHONE is phone number in international format.
+# Like +4123456789.
+TG_PHONE=your_telegram_phone_number
+
+# APP_HASH, APP_ID is from https://my.telegram.org/.
+APP_ID=your_app_id
+APP_HASH=your_app_hash
+
 SOURCE_GROUP_ID=-123456789
 TARGET_GROUP_ID=-123456789