Entity Framework - System.Configuration error

So, I'm making a xamarin forms app, and I have a web service that share my data models to each other.
It all works fine for my web service, but when I try to build my app, I get the following error

Can not resolve reference: System.Configuration, referenced by AppName > AppName.Models > EntityFramework. Please add a NuGet package or assembly reference for System.Configuration, or remove the reference to AppName.

I've installed the Entity framework nugget on my app, I've tryed to instal system.configuration.ConfigurationManager but I always get the same error... How can I resolve this since I need the entity framework for my Model's dll?