public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();
        services.AddNSwagSwagger(new NSwagConfig { ApiGroupNames = new[] { "test_V1" } });
        services.AddNSwagSwagger(new NSwagConfig { ApiGroupNames = new[] { "test_V2" } });
        services.AddNSwagSwagger(new NSwagConfig { });
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        app.UseNSwagSwaggerUI();
        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
    }
}