No userProperty info back to client in publish ack message.

[fighting300]

Hello, there,
when i publish a message with userProperty, I didnot get the userProperty from message ack body. why?
I use mqtt protocal 5.0, and the code is blow

`
_pubProp = [[MqttPublishProperties alloc] initWithContentType:@"JSON"];
[_pubProp setUserProperty:@{@"uuid": uuid}];
[_mqtt5 publish:@"dragonTopic/3" withString:@"test" qos:CocoaMQTTQoSQos1 DUP:YES retained:YES properties:_pubProp];

func didReceive(_ reader: CocoaMQTTReader, puback: FramePubAck) {
    printDebug("RECV: \(puback) test2 \(String(describing: puback.pubAckProperties?.userProperty)) test1 \(String(describing: puback.userProperties))")
    deliver.ack(by: puback)

    delegate?.mqtt5(self, didPublishAck: puback.msgid, pubAckData: puback.pubAckProperties ?? nil)
    didPublishAck(self, puback.msgid, puback.pubAckProperties ?? nil)
}

`
I want get the same user property what i send， how can i get to this result。
thanks for giving help to me

[JaylinYu]

Broker's job not sdk.