readexactly() called while another coroutine is already waiting for incoming data，what's wrong？

[lddlww]

my code is：

import csv
import asyncio
import aiomysql
import time
import sys
import argparse

parser = argparse.ArgumentParser(description="A python program to import and compare csv data with mysql database.")
parser.add_argument("--host", type=str, default="172.27.2.19", help="The host name of the database.")
parser.add_argument("--user", type=str, default="prog_test", help="The user name of the database.")
parser.add_argument("--password", type=str, default="abcd.1234", help="The password of the database.")
parser.add_argument("--db", type=str, default="test", help="The name of the database.")
parser.add_argument("--table", type=str, default="t1", help="The name of the table.")
parser.add_argument("action", type=str, choices=["load", "compare"], help="The action to perform: load or compare.")
load_group = parser.add_argument_group("load", "Arguments for loading csv data to database")
load_group.add_argument("--csv", type=str, required=False, help="The path of the csv file to import. Only valid for load action.")
compare_group = parser.add_argument_group("compare", "Arguments for comparing csv data with database")
compare_group.add_argument("--new_csv", type=str, required=False, help="The path of the new csv file to compare. Only valid for compare action.")
compare_group.add_argument("--output", type=str, default="output.csv", help="The path of the output csv file to write. Only valid for compare action.")

args = parser.parse_args()

DB_HOST = args.host
DB_USER = args.user
DB_PASSWORD = args.password
DB_NAME = args.db
DB_TABLE = args.table

ACTION = args.action

async def insert_batch(batch, conn):
    cur = await conn.cursor()
    sql = f"insert into {DB_TABLE} (id, name, identified_id) values (%s, %s, %s)"
    try:
        await cur.executemany(sql, batch)
        await conn.commit()
    except Exception as e:
        print(e)
    finally:
        await cur.close()

async def import_csv2():
    start = time.time()
    pool = await aiomysql.create_pool(host=DB_HOST, user=DB_USER, password=DB_PASSWORD, db=DB_NAME)
    CSV_FILE=args.csv
    with open(CSV_FILE, "r", encoding="utf-8") as f:
        reader = csv.reader(f)
        next(reader)
        tasks = []
        batch = []
        for row in reader:
            batch.append(row)
            if len(batch) == 3:
                conn = await pool.acquire()
                task = asyncio.create_task(insert_batch(batch, conn))
                tasks.append(task)
                pool.release(conn)
                batch = []
        if batch:
            conn = await pool.acquire()
            task = asyncio.create_task(insert_batch(batch, conn))
            tasks.append(task)
            pool.release(conn)
        await asyncio.gather(*tasks)
    pool.close()
    await pool.wait_closed()
    end = time.time()
    print(f"Imported {CSV_FILE} to {DB_NAME}.{DB_TABLE} in {end - start} seconds.")

def main():
    loop = asyncio.get_event_loop()
    if ACTION == "load":
        loop.run_until_complete(import_csv2())
    else:
        print(f"Invalid action: {ACTION}")
    loop.close()

if __name__ == "__main__":
    main()

when i run python load.py --csv load.csv load ,it throws errors:

readexactly() called while another coroutine is already waiting for incoming data

test.t1 table structure:

CREATE TABLE `t1` (
  `id` int NOT NULL AUTO_INCREMENT,
  `name` varchar(50) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `identified_id` varchar(100) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `name` (`name`,`identified_id`)
) ENGINE=InnoDB

how can i do to fix it?