asyncio.wait_for didn't cancel the task - python-3.x

Question

After the asyncio.wait_for timeout, the task was not cancelled
The script below is the minimized script to reproduce it. The tcp server just sent two chars after 100 seconds later after client connected
import sys
import asyncio
import socket
async def test_single_call():
reader, writer = await asyncio.open_connection(host='127.0.0.1', port=8888)
try:
msg = await asyncio.wait_for(reader.read(1), timeout=3)
print("Unexcepted message received:" , msg, file=sys.stderr)
assert False
except asyncio.TimeoutError:
pass
msg = await reader.read(1)
loop = asyncio.get_event_loop()
loop.run_until_complete(test_single_call())
loop.close()
The tcpclient(code above) is expected to timeout 3 seconds later, and read again after that; but it seems the task was not cancelled after it was timeout. My python version is 3.6.9
Traceback (most recent call last):
File "tcpclient.py", line 17, in <module>
loop.run_until_complete(test_single_call())
File "/usr/lib/python3.6/asyncio/base_events.py", line 484, in run_until_complete
return future.result()
File "tcpclient.py", line 14, in test_single_call
msg = await reader.read(1)
File "/usr/lib/python3.6/asyncio/streams.py", line 634, in read
yield from self._wait_for_data('read')
File "/usr/lib/python3.6/asyncio/streams.py", line 452, in _wait_for_data
'already waiting for incoming data' % func_name)
RuntimeError: read() called while another coroutine is already waiting for incoming data
I also uploaded the tcp server here

Answer 1

For Linux Python 3.6, it had this issue. two options:
Upgrade to Python 3.8 or 3.9
Replace the open_connection and StreamReader with loop.sock_connet, loop.sock_recv, loop.sock_sendall
eg:
import sys
import asyncio
import socket
async def test_single_call(loop):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock = await loop.sock_connect(sock, server_address)
try:
msg = await asyncio.wait_for(loop.sock_recv(sock, 1), timeout=3)
print("Unexcepted message received:" , msg, file=sys.stderr)
assert False
except asyncio.TimeoutError:
pass
msg = await loop.sock_recv(sock, 1)
loop = asyncio.get_event_loop()
loop.run_until_complete(test_single_call(loop))
loop.close()