Cursor.execute() freezes + Pool.wait_closed() blocks after Pool.close()

Dear contributors,

do you have any ideas why execute can at all freeze??

At the time it blocks, **pgAdmin** says that connection is `idle` and Wait event is `Client: ClientRead`
```
wapp["state"]["db"] = await aiopg.create_pool(host=wapp["config"]["db-ip"],
database=wapp["config"]["db-name"],
user=wapp["config"]["db-usr"],
password=wapp["config"]["db-pwd"],
timeout=wapp["config"]["db-connect-timeout"])

async with wapp["state"]["db"] as _dbconn:
# Get cursor
_c = await _dbconn.cursor()
# Get all table contents
await _c.execute("SELECT * FROM fa_user_timestamps;")
# Fetch all results
_rc = _c.rowcount
_sm = _c.statusmessage
if _rc != -1:
_qr = await _c.fetchall()
```
In the end, after handling SIGTERM via `loop.add_signal_handler()` and calling `Pool.close()` - the `await Pool.wait_closed()` as well blocks.

Am I doing something wrong??