Xamarin forms nuget package on a .net standard portable project

Hi,

I have a .net standard portable project and I'm trying to add Xamarin forms nuget package. I get the following error:

"Package Xamarin.Forms 2.3.1.114 is not compatible with netstandard1.6"

That's my project json file:

{
"supports": {},
"dependencies": {
"Microsoft.NETCore.Portable.Compatibility": "1.0.1",
"NETStandard.Library": "1.6.0",
"OpenTK.NETCore": "1.1.2364.6424"
},
"frameworks": {
"netstandard1.6": {}
}
}

Any ideas how to fix it?