public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc(options =>
            {
                options.Filters.Add(new AutoValidateAntiforgeryTokenAttribute());
            });
        }

        public void Configure(IApplicationBuilder app)
        {
            app.UseMvcWithDefaultRoute();
        }
    }

    public class TestController : Controller
    {
        [HttpGet]
        public IActionResult Index()
        {
            return View();
        }

        [HttpPost, IgnoreAntiforgeryToken]
        public IActionResult Index(string test)
        {
            return Content("OK");
        }
    }

<form asp-antiforgery="false">
    <button>Submit</button>
</form>