channel_chat_created is always null

[bobogavin]

Message field channel_chat_created document is :
Optional. Service message: the channel has been created. This field can't be received in a message coming through updates, because bot can't be a member of a channel when it is created. It can only be found in reply_to_message if someone replies to a very first message in a channel.

so I think when we reply Channel created message, we should receive replied message channel_chat_created is true, but is still null

[Stas Parshin]

I can only suggest you to debug Telegram API requests and responses and check HTTP logs.
bot = new TelegramBot.Builder(token()).debug().build();

If there is a channel_chat_created field in HTTP raw response and library shows it as null then it's a bug and we can fix it.
But if Telegram doesn't send this field then nothing we can do