Program.cs

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

namespace GameServer;
class Program
{
    static async Task Main(string[] args)
    {
        var host = new HostBuilder()
            .ConfigureAppConfiguration((hostingContext, config) =>
            {
                var env = hostingContext.HostingEnvironment;
                config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);
            })
            .ConfigureLogging(logging =>
            {
                logging.SetMinimumLevel(LogLevel.Debug);
                logging.AddConsole();
            })
            .ConfigureServices((hostContext, services) =>
            {
                services.Configure<ServerOption>(hostContext.Configuration.GetSection("ServerOption"));
                services.AddHostedService<MainServer>();
            })
            .Build();

        await host.RunAsync();
    }
}