Actually I am trying to integrate the GSA with AEM 6.4 but I am facing the issues. Is it still supported ?
Isn't GSA decomissioned by Google?
If Google decomissioned it - i would not use it in AEM to build projects.
update - GSA Discontinued: Google, the Google Search Appliance, and Beyond | Search Technologies
Google is not selling any more new licenses as per below link, we moved out of GSA last year.
Google Search Appliance 7.6 - Google Enterprise Search
Google is not selling licenses anymore.
We stopped using it few months back instead started using something else.
Instead of GSA, you can consider using Solr.