unload event in documents are deprecated

Chrome deprecating unload events now. signalr JS files uses this event ( unload ). Deprecation causes errors in dev console. see: https://developer.chrome.com/docs/web-platform/deprecating-unload

Alternatives for the unload event are visibilitychange and pagehide. I think these should be used instead of unload event if possible.

As a workaround for now i added default headers to my Web.config to enable unload functionality. <add name="Permissions-Policy" value="unload=(self)" />

Issue happens in latest version too.