webserver在IHostedService启动之前开始处理请求

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Hosting;
using System.Threading;
using System.Threading.Tasks;

public class CustomWebServer : IHostedService
{
    private readonly IWebHost _webHost;

    public CustomWebServer(IWebHost webHost)
    {
        _webHost = webHost;
    }

    public Task StartAsync(CancellationToken cancellationToken)
    {
        return _webHost.StartAsync(cancellationToken);
    }

    public Task StopAsync(CancellationToken cancellationToken)
    {
        return _webHost.StopAsync(cancellationToken);
    }
}

public class Startup
{
    public void Configure(IApplicationBuilder app)
    {
        app.UseRouting();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapGet("/", async context =>
            {
                await context.Response.WriteAsync("Hello, World!");
            });
        });
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        var webHost = new WebHostBuilder()
            .UseKestrel()
            .UseStartup<Startup>()
            .Build();

        var customWebServer = new CustomWebServer(webHost);

        var host = Host.CreateDefaultBuilder(args)
            .ConfigureServices((hostContext, services) =>
            {
                services.AddSingleton<IHostedService>(customWebServer);
            })
            .Build();

        host.Run();
    }
}