I also checked using 3.8 (built from commit 1f58f4fa6a0e3c60cee8df4a35c8dcf3903acde8), and it works there, so it looks as if 3.7 is the problem.

> VENV38\Scripts\python.exe --version
Python 3.8.0a2+

> VENV38\Scripts\python.exe mp_queue_example.py
main, pid=8284, executable=D:\dev\eva_v_next\VENV38\Scripts\python.exe
process_worker, pid=16396, executable=D:\dev\cpython\PCbuild\win32\python.exe
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