there is a warn when I add this
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: java.net.ConnectException: Connection refused: connect
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at java.net.DualStackPlainSocketImpl.connect0(Native Method)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at java.net.PlainSocketImpl.connect(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at java.net.SocksSocketImpl.connect(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at java.net.Socket.connect(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at sun.security.ssl.SSLSocketImpl.connect(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at sun.security.ssl.BaseSSLSocketImpl.connect(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at sun.net.NetworkClient.doConnect(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at sun.net.
www.http.HttpClient.openServer(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at sun.net.
www.http.HttpClient.openServer(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at sun.net.
www.protocol.https.HttpsClient.<init>(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at sun.net.
www.protocol.https.HttpsClient.New(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at sun.net.
www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at sun.net.
www.protocol.http.HttpURLConnection.plainConnect0(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at sun.net.
www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at sun.net.
www.protocol.https.AbstractDelegateHttpsURLConnection.connect(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at sun.net.
www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at sun.net.
www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at sun.net.
www.protocol.https.HttpsURLConnectionImpl.getInputStream(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at java.net.URL.openStream(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at hu.montlikadani.tablist.bukkit.utils.UpdateDownloader$1.run(UpdateDownloader.java:36)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftTask.run(CraftTask.java:64)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at org.bukkit.craftbukkit.v1_12_R1.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:50)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at com.destroystokyo.paper.ServerSchedulerReportingWrapper.run(ServerSchedulerReportingWrapper.java:22)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
[16:03:24] [Craft Scheduler Thread - 14/WARN] []: at java.lang.Thread.run(Unknown Source)