Migrate ASP.NET Core 1.1 with 4.6.1 class library to ASP.NET Core 2.0

We have a REST API written in ASP.NET Core 1.1 and it's using an old 4.6.1 class library.

I now have to make updates to this solution and I figured it's probably best to upgrade it to ASP.NET Core 2.0. 

Is it possible to use the class library as it is with ASP.NET Core 2.0? Do we have to migrate it? Same class library is still being used by another application we have that is webforms so it would be best if we didn't have to migrate it.