OWIN, take 2

OwinDraft2.cs

using System.Collections.Generic;
using System.Threading.Tasks;

namespace Owin
{
    public struct OwinResponse
    {
        public string Status;
        public IDictionary<string, IEnumerable<string>> Headers;
        public IEnumerable<object> Body;
    }

    public delegate Task<OwinResponse> OwinApp(IDictionary<string, object> env);
}