Your build breaks with errors about being unable to copy dll files from packages\Microsoft.Net.Compilers to bin\roslyn\ looking like on screenshot below? Here is workaround broken build in Visual Studio.
Way to unblock and continue working is to hit Alt+Control+Del, open Task Manager and kill VBCSCompiler.exe
After doing that, your build will succeed and you are good to go.
This is not the final solution for the problem. It will unblock you to continue working, but VBCSCompiler will get loaded again eventually and build might break again. Still, until the lasting solution is found, happy coding. Just go!