如何在.NET Core2.2中为SignalR配置JsonOptions？

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.AspNetCore.SignalR;
using Newtonsoft.Json;

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        // 配置JsonSerializerSettings
        var jsonSettings = new JsonSerializerSettings
        {
            DateFormatHandling = DateFormatHandling.IsoDateFormat,
            NullValueHandling = NullValueHandling.Ignore,
            // 添加其他需要的设置
        };

        // 配置SignalR使用自定义的JsonSerializerSettings
        services.AddSignalR()
            .AddJsonProtocol(options =>
            {
                options.PayloadSerializerSettings = jsonSettings;
            });

        // 其他服务配置...
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseRouting();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapHub<ChatHub>("/chatHub");
        });
    }
}

public class ChatHub : Hub
{
    public async Task SendMessage(string user, string message)
    {
        await Clients.All.SendAsync("ReceiveMessage", user, message);
    }
}