No “up to date” message when running the latest ve

I'm trying to use Sparkle with Qt (binding for Go) app.

sparkle.m:

#import <Headers/SUUpdater.h>

static SUUpdater* updater = nil;

void sparkle_checkUpdates()
{
    if (!updater) {
        updater = [[SUUpdater sharedUpdater] retain];
    }

    [updater setUpdateCheckInterval:3600];
    [updater checkForUpdatesInBackground];
}

sparke.go:

// +build darwin windows

package main

/*
#cgo CFLAGS: -I ${SRCDIR}/Sparkle.framework
#cgo LDFLAGS: -F ${SRCDIR} -framework Sparkle

void sparkle_checkUpdates();
*/
import "C"

func sparkle_checkUpdates() {
    C.sparkle_checkUpdates()
}

And in main.go, I added a menu to call that func:

package main

import (
    "github.com/therecipe/qt/widgets"
)

func main() {
    action := widgets.NewQMenuBar(nil).AddMenu2("").AddAction("Check for Updates...")
    // http://doc.qt.io/qt-5/qaction.html#MenuRole-enum
    action.SetMenuRole(widgets.QAction__ApplicationSpecificRole)
    action.ConnectTriggered(func(bool) { sparkle_checkUpdates() })
}

It is working fine when there is an update: download, extract, install, relaunch, ... But when running the latest version, click "Check for Updates..." menu and nothing happens. There is no popup said that we are up-to-date, something like this: In Console, I only see this:

[3 <private> stream, pid: 90977, url: https://example.com/appcast.xml, traffic class: 200, tls] cancelled
    [3.1 70A1F65B-7E7A-4ED2-AB8B-A21621ED7658 <private>.58040<-><private>]
    Connected Path: satisfied (Path is satisfied), interface: en0, ipv4, dns
    Duration: 0.497s, DNS @0.000s took 0.001s, TCP @0.003s took 0.051s, TLS took 0.113s
    bytes in/out: 4481/675, packets in/out: 6/3, rtt: 0.053s, retransmitted packets: 0, out-of-order packets: 0

appcast.xml:

<?xml version="1.0" standalone="yes"?>
<rss xmlns:sparkle="http://www.andymatuschak.org/xml-namespaces/sparkle" version="2.0">
  <channel>
    <title>Premium VPN</title>
    <item>
      <title>1.0.0.2905</title>
      <pubDate>Tue, 11 Dec 2018 11:09:10 +0800</pubDate>
      <sparkle:minimumSystemVersion>10.7</sparkle:minimumSystemVersion>
      <enclosure url="https://example.com/x.zip" sparkle:version="1.0.0.2905" sparkle:shortVersionString="1.0.0.2905" sparkle:edSignature="x" length="104408678" type="application/octet-stream"/>
    </item>
  </channel>
</rss>

Info.plist:

    <key>SUFeedURL</key>
    <string>https://example.com/appcast.xml</string>
    <key>SUPublicEDKey</key>
    <string>x</string>

Did I miss something?

Look carefully at the checkForUpdatesInBackground:

/*!
 Checks for updates, but does not display any UI unless an update is found.

 This is meant for programmatically initating a check for updates. That is,
 it will display no UI unless it actually finds an update, in which case it
 proceeds as usual.

 If automatic downloading of updates it turned on and allowed, however,
 this will invoke that behavior, and if an update is found, it will be downloaded
 in the background silently and will be prepped for installation.

 This will not find updates that the user has opted into skipping.
 */
- (void)checkForUpdatesInBackground;

So, with this method, the UI will only be shown if an update is found.

What I want is checkForUpdates:

/*!
 Explicitly checks for updates and displays a progress dialog while doing so.

 This method is meant for a main menu item.
 Connect any menu item to this action in Interface Builder,
 and Sparkle will check for updates and report back its findings verbosely
 when it is invoked.

 This will find updates that the user has opted into skipping.
 */
 - (IBAction)checkForUpdates:(id)sender;