How to immediately find out in a Telegram bot that a user has unsubscribed from the channel?

Question

Bots

There is a bot with an audience of 10,000 people. The bot has a condition that the user must always be subscribed to the channel, but there is one problem: if the user has unsubscribed from the channel, his status must be changed immediately.

I tried using a timer to run a function to check everyone, but this slows down the bot very much.

How to be?

Answer 1

So do a check before sending a message from the bot to the user. If subscribed - allow commands, else { tg('sendMessage', "Well, I SUBSCRIBE QUICKLY")
check like this:
How to check a subscription to a telegram channel?