Entity Framework Core 2.0.0 Migrations in different project

I have two projects.

1) .NetCore Console App

• Microsoft.EntityFrameworkCore.Tools 2.0.0
• Microsoft.EntityFrameworkCore.SqlServer 2.0.0
• Microsoft.Extensions.Configuration.Json 2.0.0

I have a an entry point

class Program
{
    private static IConfiguration Configuration { get; set; }

    static void Main(string[] args)
    {
        IConfigurationRoot configurationRoot = new ConfigurationBuilder()
            .AddJsonFile($"appsettings.json", true, true)
            .Build();

        Configuration = configurationRoot;

        // create service collection
        var serviceCollection = new ServiceCollection();
        ConfigureServices(serviceCollection);

        // create service provider
        serviceCollection.BuildServiceProvider();
    }

    private static void ConfigureServices(ServiceCollection serviceCollection)
    {
        string connectionString = Configuration.GetConnectionString("DefaultConnection");
        serviceCollection.AddDbContext<MyDbContext>(options => options.UseSqlServer(connectionString));
    }
}

and an appsettings.json

{
  "ConnectionStrings": {
    "DefaultConnection": "****"
  }
}

2) .NetStandard Lib (contains DbContext)

• Microsoft.EntityFrameworkCore 2.0.0
• Microsoft.EntityFrameworkCore.Tools 2.0.0
• Microsoft.EntityFrameworkCore.SqlServer 2.0.0

I want to be able to create a migration script using dotnet ef migrations add [NAME] and i've worked out if I run the command whilst in the lib folder I can target a startup project to run the migrations.

D:\Lib> dotnet ef migrations add InitialCreate -s ..\ConsoleApp\

I managed to get this working by adding a class in the same folder as MyDbContext that implements IDesignTimeDbContextFactory<MyDbContext> I can add a connection string and it runs perfectly.

public class MyDbContextFactory : IDesignTimeDbContextFactory<MyDbContext>
{
    public MyDbContext CreateDbContext(string[] args)
    {
        DbContextOptionsBuilder<MyDbContext> builder = new DbContextOptionsBuilder<MyDbContext>();
        builder.UseSqlServer("****", optionsBuilder => optionsBuilder.MigrationsAssembly(typeof(MyDbContext).GetTypeInfo().Assembly.GetName().Name));
        return new MyDbContext(builder.Options);
    }
}

The problem I have is I want to use the connection string from within the console app's appsettings.json.

Is it possible and how can I do it?

Thanks in advance.