Segfault and/or StopIteration error when executing queries in multithreading app

import argparse

import random

from concurrent.futures import ThreadPoolExecutor, ProcessPoolExecutor, as_completed

import time

import traceback

from couchbase.auth import PasswordAuthenticator

from couchbase.cluster import Cluster, ClusterOptions, QueryOptions

from couchbase.options import LockMode

class CouchbaseConfig:

    uri = "couchbase://localhost"

    user = "YourUsername"

    password = "YourPassword"

    cert_path = None

sql = 'SELECT * FROM `travel-sample`.inventory.airport WHERE airportname = $1 LIMIT 10'

def get_couchbase():

    cb = Cluster(CouchbaseConfig.uri, ClusterOptions(

            PasswordAuthenticator(CouchbaseConfig.user, CouchbaseConfig.password, CouchbaseConfig.cert_path),

            # unlock_gil=True,

            lockmode=LockMode.WAIT

        )

    )

    return cb

# cb = get_couchbase()

def run_query_loop(cnt=1000):

    cb = get_couchbase()

    print(id(cb))

    airportnames = ["Calais Dunkerque", "Les Loges", "Bray", "abc", "efg", "hjk"]

    for _ in range(cnt):

        try:

            airportname = random.choice(airportnames)

            result = cb.query(sql, QueryOptions(metrics=True, positional_parameters=(airportname,)))

            for row in result:

            # for row in result.rows():

                # print("Found row: {}".format(row))

                pass

        except:

            print(f"sql => {sql}, args => {airportname}")

            traceback.print_exc()

            raise

    return "success"

def get_args():

    parser = argparse.ArgumentParser()

    parser.add_argument('workers', metavar='int', type=int, help='number of thread/prcoess')

    parser.add_argument('q_count', metavar='int', type=int, help='run n1ql query times')

    parser.add_argument('use_thread', metavar='int', type=int, default=0, help='use thread to run task')

    return parser.parse_args()

if __name__ == '__main__':

    args = get_args()

    bt = time.time()

    futs = []

    if args.use_thread:

        with ThreadPoolExecutor(args.workers) as pool:

            for _ in range(args.workers):

                futs.append(pool.submit(run_query_loop, args.q_count))

    else:

        with ProcessPoolExecutor(args.workers) as pool:

            for _ in range(args.workers):

                futs.append(pool.submit(run_query_loop, args.q_count))

    for fut in as_completed(futs):

        exc = fut.exception()

        if exc:

            print("future error ===> ", exc)

        else:

            print("future result ===> ", fut.result())

    print("main end: ", time.time() - bt)

    # run example:

    # python test_n1ql.py 4 1000 1