client.go
func (c *Client) Depart(channel string) {
	if c.connActive.get() {
		go c.send(fmt.Sprintf("PART #%s", channel))
	}

	c.channelsMtx.Lock()
	delete(c.channels, channel)
	c.channelUserlistMutex.Lock()
	delete(c.channelUserlist, channel)
	c.channelUserlistMutex.Unlock()
	c.channelsMtx.Unlock()
}
func (c *Client) Depart(channel string) {
	if c.connActive.get() {
		go c.send(fmt.Sprintf("PART #%s", channel))
	}

	c.channelsMtx.Lock()
	delete(c.channels, channel)
	c.channelUserlistMutex.Lock()
	delete(c.channelUserlist, channel)
	c.channelUserlistMutex.Unlock()
	c.channelsMtx.Unlock()
}
// Depart leave a twitch channel