How I can use multiprocessing with upickled module variable?

[AlekseyPython]

Python 3.7.1

I use multiprocessing.Pool for paralleling my code, and it work good. But when I add contextvars in working module (for my coroutines, which I created 2 for each process):

import contextvars
line_var = contextvars.ContextVar('my_var')

def my_func():
    line = 1
    line_by_ticker_var.set(line)
    line2 = line_var.get()

I got this error:

Error:
multiprocessing.pool.MaybeEncodingError: Error sending result: '<multiprocessing.pool.ExceptionWithTraceback object at 0x7fe233cccf90>'. Reason: 'TypeError("can't pickle ContextVar objects")'

How can I use multiprocessing and asynchrony (with the necessary module contextvars) at the same time?