how to run task at scheduled time with RabbitMQ

RabbitMQ is not a task scheduler, even though the documentation talks about “scheduling” a task. You might consider using something like cron. You could also use a library like sched to build a scheduler in a Python process.

FYI It looks like this question has already been answered:
Delayed message in RabbitMQ

RabbitMQ has a plugin for delayed messages.

Using this plugin, the messages can be delivered to the respective queues after a certain delay. Thanks to this plugin, you can use RabbitMQ as a scheduler, even though it’s not a task scheduler by nature.