services.AddHostedService

I have an issue been working on for a few hours with little progress. I have a need for creating services based off a dynamic configuration. IE lets say I have 5 classes that inherit from IHostedService and they can easily be started using services.AddHostedService<classname>(). The issue I have however is I need to be able to dynamically setup these services. IE:

public static void Register(IServiceCollection services, IConfiguration configuration)
{
    foreach (var service in configuration.GetSection("services").GetChildren())
    {
        foreach (var consumer in service.GetChildren())
        {
            var className = configuration.GetValue<string>("className");
            var assemblyName = configuration.GetValue<string>("assemblyName");

            System.Type classType = System.Type.GetType(className + ", " + assemblyName);

            services.AddHostedService<classType>();
        }
    }
}

settings file would look like this

{"services": {"service1": {"className": "class.name.something","assemblyName": "test.assembly",
    },"service2": {"className": "some.other.class.testing","assemblyName": "something.assembly",
    },"service3": {"className": "this.is.path.to.class.in.assembly","assemblyName": "test.something",
    }
  }
}

The problem I have is:
services.AddHostedService<classType>();

that is not valid syntax, I cant seem to figure out how to dynamically provide a class type to AddHostedService, it appears you have to use a concrete class. 

any ideas? thanks!