The package is not fully compatible with dotnetcore 2.0 for now.
eg, for 'Microsoft.AspNet.WebApi.Client'
it maybe supported in version (5.2.4).
See Consume new Microsoft.AspNet.WebApi.Client.5.2.4 package for details.
You could try the standard Client package as Federico mentioned.
If that still not work, then as a workaround you can only create a Console App (.Net Framework)
instead of the .net core 2.0 console app.
Reference this thread: Microsoft.AspNet.WebApi.Client supported in .NET Core or not?