System.Threading.Channels + Telegram.Bot polling

ChannelPolling.cs

using System;
using System.Threading;
using System.Threading.Channels;
using System.Threading.Tasks;
using Telegram.Bot;
using Telegram.Bot.Types;

namespace ChannelPolling
{
    internal static class Program
    {
        static Channel<Update> updateChannel;
        static ITelegramBotClient botClient;

        static async Task Main(string[] args)
        {
            updateChannel = Channel.CreateUnbounded<Update>(
                new UnboundedChannelOptions()
                {
                    SingleWriter = true,
                    SingleReader = true
                });

            botClient = new TelegramBotClient("123456:ABCDEFGHI");

            using var cts = new CancellationTokenSource();

            var producer = Task.Run(async () => await Producer(cts));
            var consumer = Task.Run(async () => await Consumer());

            Console.WriteLine("Start receiving updates. Press Enter to stop...");
            Console.ReadLine();
            cts.Cancel();

            await Task.WhenAll(producer, consumer);
        }

        private static async Task Consumer()
        {
            Console.WriteLine("Starting consumer...");

            await foreach (var update in updateChannel.Reader.ReadAllAsync())
            {
                Console.WriteLine($"{update.Id.ToString()} {update.Type} {update.Message?.Text}");
            }

            Console.WriteLine("Stopping consumer...");
        }

        private static async Task Producer(CancellationTokenSource cts)
        {
            Console.WriteLine("Starting producer...");

            var offset = -1;

            while (!cts.IsCancellationRequested)
            {
                var updates = await botClient.GetUpdatesAsync(offset: offset);
                offset = updates.Length > 0 ? updates[^1].Id + 1 : -1;

                foreach (var update in updates)
                {
                    await updateChannel.Writer.WriteAsync(update);
                }
            }

            Console.WriteLine("Stopping producer...");

            updateChannel.Writer.Complete();
        }
    }
}