SocketModeApp (JavaWebSocket) does not support proxy with username:password

How do you configure proxy for Bolt Java SDK?

Able to set url using below but getting auth error

SlackConfig config = new SlackConfig();
    config.setProxyUrl("http://myproxy");

    Slack slack = Slack.getInstance(config);
    
    SocketModeClient client = slack.socketMode(appToken, SocketModeClient.Backend.JavaWebSocket);

    SocketModeApp socketModeApp = new SocketModeApp(
        client,
        app
    );
    socketModeApp.start();

The Slack SDK version

[INFO] +- com.slack.api:bolt🫙1.9.0:compile
[INFO] | +- com.slack.api:slack-api-model🫙1.9.0:compile
[INFO] | +- com.slack.api:slack-api-client🫙1.9.0:compile
[INFO] | - com.slack.api:slack-app-backend🫙1.9.0:compile
[INFO] +- com.slack.api:bolt-servlet🫙1.9.0:compile
[INFO] +- com.slack.api:bolt-jetty🫙1.9.0:compile
[INFO] +- com.slack.api:bolt-socket-mode🫙1.9.0:compile

Java Runtime version

java version "1.8.0_271"
Java(TM) SE Runtime Environment (build 1.8.0_271-b09)
Java HotSpot(TM) 64-Bit Server VM (build 25.271-b09, mixed mode)

OS info

ProductName: Mac OS X
ProductVersion: 10.15.7
BuildVersion: 19H1217
Darwin Kernel Version 19.6.0: Thu May 6 00:48:39 PDT 2021; root:xnu-6153.141.33~1/RELEASE_X86_64

Expected result:

Connected to slack API

Actual result:

Failed to call auth.test API (error: Failed to authenticate with proxy)
java.io.IOException: Failed to authenticate with proxy