Handling async in Rx.

ReqresReader.cs

namespace PrimeFactors
{
    using System;
    using System.Net.Http;
    using System.Reactive.Linq;
    using System.Threading;
    using System.Threading.Tasks;

    class ReqresReader
    {
        private readonly HttpClient _client = new HttpClient();

        private async Task<IObservable<User>> IdWithPossibleWait(int i, CancellationToken tok)
        {
            Task<UsersListResponse> theTask = (await _client.GetAsync($"https://reqres.in/api/users?page={i}", tok)).Content.ReadAsAsync<UsersListResponse>(tok);
            return Observable.FromAsync(() => theTask).SelectMany(userListResp => userListResp.Data);
        }

        public void Do()
        {
            CancellationTokenSource source = new CancellationTokenSource();
            var observable = Observable.Range(1, 2).SelectMany(async (i, tok) => await IdWithPossibleWait(i, tok)).Merge();
            observable.Subscribe(Console.WriteLine, source.Token);
            Console.ReadKey();
            source.Cancel();
        }
    }
}