Visual Studio\'s Go To Definition is disabled and F12 doesn\'t work. Other commands like Alt-F12 may continue working.
I faced the same Issue in my Visual Studio 2019 version.I followed the below Steps:
Go to references folder in the solution.
Click on Manage Nuget packages.
Click on Browse.
Search for 'Microsoft.Net.Compilers'.
Click on Update.
This Worked for me.