offset.cs

public class Subscriber : ISubscribeSynchronousToAll
	{
		private readonly StreamsDBClient _client;
		private readonly string _assemblyName;

		public Subscriber(StreamsDBClient client)
		{
			_client = client;
			_assemblyName = Assembly.GetEntryAssembly().GetName().Name;
		}

		public async Task HandleAsync(IReadOnlyCollection<IDomainEvent> domainEvents, CancellationToken cancellationToken)
		{
			var offset = await GetOffset();
			offset += domainEvents.Count;
			await SetOffset(offset);
		}

		private async Task SetOffset(long offset)
		{
			var messageInput = new MessageInput
			{
				ID = Guid.NewGuid().ToString(),
				Value = Encoding.UTF8.GetBytes(offset.ToString()),
				Type = "offset"
			};

			await _client.DB().AppendStream(_assemblyName, messageInput);
		}

		public async Task<long> GetOffset()
		{
			var (message, found) = await _client.DB().ReadLastMessageFromStream(_assemblyName);

			if (!found)
			{
				return 0;
			}

			return long.Parse(Encoding.UTF8.GetString(message.Value));
		}
	}