org.apache.dubbo.remoting.exchange.support.DefaultFuture#closeChannel doesn't work as expected since the channel instances to be compared do not have correct equals() implementation:

```java
 public static void closeChannel(Channel channel) {
        for (Map.Entry<Long, Channel> entry : CHANNELS.entrySet()) {
            if (channel.equals(entry.getValue())) { // in netty4, channel is NettyChannel, but entry.getValue() is NettyClient, equals will return false.
                DefaultFuture future = getFuture(entry.getKey());
                if (future != null && !future.isDone()) {
                    Response disconnectResponse = new Response(future.getId());
                    disconnectResponse.setStatus(Response.CHANNEL_INACTIVE);
                    disconnectResponse.setErrorMessage("Channel " +
                            channel +
                            " is inactive. Directly return the unFinished request : " +
                            future.getRequest());
                    DefaultFuture.received(channel, disconnectResponse);
                }
            }
        }
    }
```

This is the root cause of issue 1 in  #1968.
result = prime * result + ((channel == null) ? 0 : channel.hashCode());
        return result;
    }
    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        NettyChannel other = (NettyChannel) obj;
        if (channel == null) {
            if (other.channel != null) {
                return false;
            }
        } else if (!channel.equals(other.channel)) {
            return false;
        }
        return true;
    }
    @Override
    public String toString() {
        return "NettyChannel [channel=" + channel + "]";
    }
}