code: func (o *ClientOptions) SetWill(topic string, payload string, qos byte, retained bool) *ClientOptions {
  	o.SetBinaryWill(topic, []byte(payload), qos, retained)
  	return o
  }
docs: // SetWill accepts a string will message to be set. When the client connects,
  // it will give this will message to the broker, which will then publish the
  // provided payload (the will) to any clients that are subscribed to the provided
  // topic.