Connection.close() while another thread runs a query hangs or crashes the interpreter #60

This work was produced with the help of language models.

Connection.close() destroys the native connection while a query on it is still running in another thread. Depending on the query, an unparameterized query hangs or aborts with heap corruption, a write segfaults, and a parameterized query makes close() wait for it. AsyncConnection.close() hits the same path, since it closes its connections before shutting down its executor.

import threading, time, ladybug as lb

conn = lb.Connection(lb.Database("db"))
q = "WITH range(1, 60000) AS r UNWIND r AS x UNWIND r AS y RETURN sum(x * y)"
threading.Thread(target=conn.execute, args=(q,)).start()
time.sleep(0.3)
conn.close()

Expected: close() returns, and the query ends with an error rather than taking the process down.
Actual: close() hangs, or the interpreter aborts or segfaults.

Reproduced with the ladybug==0.21.2 wheel on CPython 3.13.16 and 3.14.8, and on main (548c183) with CPython 3.12.

Fix: #65