What worked for me was installing .NET Core SDK 2.0 and making the following changes:
in .csproj:
change
netcoreapp1.1.0
to
netcoreapp2.0
and in global.json:
"sdk": { "version": "1.1.0" }
to
"sdk": { "version": "2.0.0" }
I didn't know how to use Chris Paton' solution