Multiprocessing pool executing synchronous - python-3.x

Question

I need an asynchronous parent process to handover function calls to a process pool.
The imports are to time consuming to spawn a new worker/process every time. So I thought to put tasks in an asyncio.queue and have a consumer listen to it and hand them off to the workers. (Sort of like how Gunicorn works but I don't want to run a webserver in order to make the calls).
However the function call seems to only be executed if I call res.get() on the response of pool.apply_async() but then it just runs as if I would call a normal synchronous for-loop.
This is my code:
#!/usr/bin/env python
import os
import time
import multiprocessing as mp
import asyncio
def f(x: list) -> int:
print(f'the pid of this process is: {os.getpid()}')
time.sleep(1)
return len(x)
def callback_func(x):
print(f'this is the callback function')
print(x)
async def consumer(queue):
with mp.Pool(processes=4) as pool:
while True:
x = await queue.get()
if x == 'stop':
break
# this makes it seem to run synchronous:
res = pool.apply_async(f, (x,))
print(res.get(), x, os.getpid())
# if I run this instead, both f() and callback_func
# are not executed.
#res = pool.apply_async(f, (x,), callback_func)
#print(x, os.getpid())
queue.task_done()
print(f'consumed')
async def producer(queue):
for i in range(20):
await queue.put([i,i+1,i+2])
# await asyncio.sleep(0.5)
await queue.put('stop')
async def main():
queue = asyncio.Queue()
input_coroutines = [consumer(queue), producer(queue)]
for f in asyncio.as_completed(input_coroutines):
try:
result = await f
print(result)
except Exception as e:
print('caught exception')
print(e)
if __name__ == "__main__":
asyncio.run(main())
What am I doing wrong?