hang.py uses the default multiprocessing start method, which was then 'fork'.  It is now 'spawn' on macOS.  And there have been many other changes.  When I run the following from IDLE, it finishes immediately.

import multiprocessing, sqlite3
def hang():
   sqlite3.connect('/tmp/foo')
if __name__ == '__main__':
   multiprocessing.Pool(2).apply_async(hang, []).get(999)
print('done')

Unless I am missing something, this should be closed as 'out of date'.