Can't detect disconnection on wifi websocket client

## Long story short
I use several esp8266 (a wifi IOT) as websocket client with aiohttp 2.3.1 websocket server .
Works perfectly but i can't detect disconnection.

## Expected behaviour
I want to detect disconnection when an esp8266 disappear.

## Actual behaviour
I detect connections and play with all clients ESP8266. The method detecst all disconnections at heartbeat delay but do nothing.
I there any solution?

## Steps to reproduce
A background loop to send a ping to all client esp8266.
WebSocketResponse instance with heartbeat param set.

## Your environment
Debian machine + Python 3.5 + aiohttp v 2.3.1