upgrade from asp.net core 2.1 to Net 6.0

I want to upgrade my project from asp.net core 2.1 to Net 6.0, I have used ".NET Upgrade Assistant" (https://dotnet.microsoft.com/en-us/platform/upgrade-assistant) from microsoft and I have fixed all the packages issues, my problem is that the build time is 3.5 minutes which is too long.