public async Task SetAsync(DeliveryDetailsDto delivery)
        {
            await _cache.SetStringAsync(GetKey(delivery.Id), JsonConvert.SerializeObject(delivery));

            // This is rather dummy - use a specialized Redis collection type instead (and full StackExchange library).
            var deliveries = await GetDeliveriesAsync();

            deliveries.Add(delivery);
            await _cache.SetStringAsync(DeliveriesKey, JsonConvert.SerializeObject(deliveries));
        }
        public Task SetAsync(DeliveryDetailsDto delivery)
        {
            var existingDelivery = _deliveries.SingleOrDefault(d => d.Id == delivery.Id);

            if (!(existingDelivery is null))
            {
                _deliveries.Remove(existingDelivery);
            }

            _deliveries.Add(delivery);

            return(Task.CompletedTask);
        }