ScaffoldingDesignTimeServices2.cs

public class ScaffoldingDesignTimeServices : IDesignTimeServices
{
    public void ConfigureDesignTimeServices(IServiceCollection services)
    {
        // Generate both context and entitites
        var options = ReverseEngineerOptions.DbContextAndEntities;

        // Register Handlebars helper
        var myHelper = (helperName: "my-helper", helperFunction: (Action<TextWriter, object, object[]>) MyHbsHelper);

        // Add Handlebars scaffolding templates
        services.AddHandlebarsScaffolding(options, myHelper);
    }

    // Sample Handlebars helper
    void MyHbsHelper(TextWriter writer, object context, object[] parameters)
    {
        writer.Write("// My Handlebars Helper");
    }
}