"unclosed transport" warning with long running client under Python 3.10

[larashores]

Describe the bug
Running Python 3.10, making any call to S3 without immediately closing the S3 client will cause the following warning to be emitted.

/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/asyncio/sslproto.py:320: ResourceWarning: unclosed transport <asyncio.sslproto._SSLProtocolTransport object at 0x10814dcc0>
  _warn(f"unclosed transport {self!r}", ResourceWarning, source=self)

Here is a minimally reproducible example:

import asyncio
import aiobotocore
import warnings

import aiobotocore.session

warnings.simplefilter("default")  # Warning only goes to console if this call is made

async def main():
    session = aiobotocore.session.get_session(
        # Replace with real tokens
        {
            "AWS_ACCESS_KEY_ID": "test",
            "AWS_SECRET_ACCESS_KEY": "test",
            "AWS_SESSION_TOKEN": "test",
        }
    )
    async with session.create_client('s3') as s3:
        print("Entered client")
        try:
            await s3.get_object(Bucket='bucket', Key="key")
        except Exception as exc:
            print("Execption", exc)
        # On Python 3.10, a ResourceWarning will appear during the sleep. If instead the client is
        # closed immediately after the get_object() call is made, the warning will not appear.
        # However, this is not desirable, as we want to share the client across multiple coroutines.
        await asyncio.sleep(10)
    
    print("Exited client")
    await asyncio.sleep(10)

if __name__ == "__main__":
    asyncio.run(main())

Running this outputs the following:

Entered client
Execption An error occurred (AccessDenied) when calling the GetObject operation: Access Denied
/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/asyncio/sslproto.py:320: ResourceWarning: unclosed transport <asyncio.sslproto._SSLProtocolTransport object at 0x104d2dcc0>
  _warn(f"unclosed transport {self!r}", ResourceWarning, source=self)
ResourceWarning: Enable tracemalloc to get the object allocation traceback
Exited client

Commenting out the first sleep, the warning disappears:

Entered client
Execption An error occurred (AccessDenied) when calling the GetObject operation: Access Denied
Exited client

Checklist

• I have reproduced in environment where pip check passes without errors
• I have provided pip freeze results
• I have provided sample code or detailed way to reproduce
• I have tried the same code in botocore to ensure this is an aiobotocore specific issue
• I have tried similar code in aiohttp to ensure this is is an aiobotocore specific issue
• I have checked the latest and older versions of aiobotocore/aiohttp/python to see if this is a regression / injection

pip freeze results

aiobotocore==2.15.1
aiohappyeyeballs==2.4.3
aiohttp==3.10.8
aioitertools==0.12.0
aiosignal==1.3.1
async-timeout==4.0.3
attrs==24.2.0
botocore==1.35.23
frozenlist==1.4.1
idna==3.10
jmespath==1.0.1
multidict==6.1.0
python-dateutil==2.9.0.post0
six==1.16.0
typing_extensions==4.12.2
urllib3==2.2.3
wrapt==1.16.0
yarl==1.13.1

Environment:

• Python Version: 3.10.11
• OS name and version: MacOS Sonoma 14.6.1

Additional context

• Running the code on Python 3.11 with the exact same dependencies will fix the issue.
• I've tried similar code in botocore and the issue doesn't occur. Though the code isn't exactly equivalent since clients are not context managers in botocore
• I've tried leaving long running sessions in aiohttp and the issue doesn't occur either.
• I see the same behavior going all the way back into aiobotocore==1.4.0 and aiohttp==3.7.0. Any earlier versions and I start to see other errors that prevents the code from running.