return err

[Harold Miao]

hi @idada

we must monitor return success or failed in application

// Broadcast to channel sessions.
func (channel *Channel) Broadcast(message Message) {
channel.broadcaster.Broadcast(channel, message)
}

change to

// Broadcast to channel sessions.
func (channel *Channel) Broadcast(message Message) error {
return channel.broadcaster.Broadcast(channel, message)
}

[达达]

修复了，多谢提醒