Multiple IServer implementations in the same app about hosting HOT 4 CLOSED

public class Program
{
    public static Task Main(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
        .UseKestrel()
        .UseMultiServer<KestrelServer, TestServer>()
        .UseStartup<Startup>()
        .Build()
        .RunAsync();
}

public class MultiServer<TServer1, TServer2> : MultiServer, IServer where TServer1 : IServer where TServer2 : IServer
{
    public MultiServer(TServer1 server1, TServer2 server2) : base(new IServer[] { server1, server2 }) { }
}

public class MultiServer : IServer
{
    public IServer[] Servers { get; }
    public IFeatureCollection Features { get; set; } = new FeatureCollection();

    public MultiServer(IServer[] servers)
    {
        Servers = servers;
        foreach (var f in servers.SelectMany(s => s.Features))
            Features[f.Key] = f.Value;
    }

    public Task StartAsync<TContext>(IHttpApplication<TContext> application, CancellationToken cancellationToken) =>
        Task.WhenAll(Servers.Select(s => s.StartAsync(application, cancellationToken)));

    public Task StopAsync(CancellationToken cancellationToken) =>
        Task.WhenAll(Servers.Select(s => s.StopAsync(cancellationToken)));

    public void Dispose()
    {
        foreach (var s in Servers)
            s.Dispose();
    }
}

public static class ServerExtensions
{
    public static IWebHostBuilder UseMultiServer<TServer1, TServer2>(this IWebHostBuilder hostBuilder) where TServer1 : class, IServer where TServer2 : class, IServer =>
        hostBuilder.ConfigureServices(services =>
        {
            services.AddSingleton<TServer1, TServer1>();
            services.AddSingleton<TServer2, TServer2>();
            services.AddSingleton<IServer, MultiServer<TServer1, TServer2>>();
        });
}

public class TestServer : IServer
{
    public Task StartAsync<TContext>(IHttpApplication<TContext> application, CancellationToken cancellationToken) => Task.CompletedTask;
    public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;
    public IFeatureCollection Features { get; } = new FeatureCollection();
    public void Dispose() { }
}