def set_will(topic, payload, retain = false, qos = 0)
      self.will_topic = topic
      self.will_payload = payload
      self.will_retain = retain
      self.will_qos = qos
    end
def set_will(topic, payload, retain = false, qos = 0)
      self.will_topic = topic
      self.will_payload = payload
      self.will_retain = retain
      self.will_qos = qos
    end
Set the Will for the client

 The will is a message that will be delivered by the server when the client dies.
 The Will must be set before establishing a connection to the server