static async IAsyncEnumerable<int> RangeAsync(int start, int count)
{
  for (int i = 0; i < count; i++)
  {
    await Task.Delay(i);
    yield return start + i;
  }
}

    [ApiController]
    [Route("[controller]")]
    public class CustomerController : ControllerBase
    {
        private readonly IDictionary<int, Customer> _customers;
        private void FillCustomerFromMemory(int countOfCustomer)
        {
            for (int CustomerId = 1; CustomerId <= countOfCustomer; CustomerId++)
            {
                _customers.Add(key: CustomerId, new Customer($"name_{CustomerId}", CustomerId));
            }
        }
        public CustomerController()
        {
            _customers = new Dictionary<int, Customer>();
            FillCustomerFromMemory(countOfCustomer : 100);
        }
        [HttpGet]
        public async Task<IEnumerable<Customer>> Get()
        {
            var output = new List<Customer>();
            while (_customers.Any(_ => _.Key % 10 == 0))
            {
                var customer = _customers.First(_ => _.Key % 10 == 0);
                output.Add(new Customer(customer.Value.Name, customer.Key));
                await Task.Delay(500);
                _customers.Remove(customer);
            }
            return output;
        }

        public class Customer
        {
            public int Id { get; private set; }

            public string Name { get; private set; }
            public Customer(string name, int id)
            {
                Name = name;
                Id = id;
            }
        }
    }

  [HttpGet]
        public async IAsyncEnumerable<Customer> Get()
        {
            while (_customers.Any(_ => _.Key % 10 == 0))
            {
                var customer = _customers.First(_ => _.Key % 10 == 0);
                yield return new Customer(customer.Value.Name, customer.Key);
                _customers.Remove(customer);
                await Task.Delay(500);
            }
        }

const int TARGET = 80;
var _httpClient = new HttpClient();
using (var response = await _httpClient.GetAsync(
    "https://localhost:7284/customer",
     HttpCompletionOption.ResponseHeadersRead))
{
    var stream = await response.Content.ReadAsStreamAsync();

    var _jsonSerializerSettings = new JsonSerializerSettings();
    var _serializer = Newtonsoft.Json.JsonSerializer.Create(_jsonSerializerSettings);

    using TextReader textReader = new StreamReader(stream);
    using JsonReader jsonReader = new JsonTextReader(textReader);

    await using (stream.ConfigureAwait(false))
    {
        await jsonReader.ReadAsync().ConfigureAwait(false);
        while (await jsonReader.ReadAsync().ConfigureAwait(false) &&
               jsonReader.TokenType != JsonToken.EndArray)
        {
            Customer customer = _serializer!.Deserialize<Customer>(jsonReader);
            if (customer.Id == TARGET)
            {
                Console.WriteLine(customer.Id + " : " + customer.Name);
                break;
            }
        }
    }
}

[HttpGet]
        public async IAsyncEnumerable<Customer> Get(CancellationToken cancellationToken)
        {
            while (!cancellationToken.IsCancellationRequested && _customers.Any(_ => _.Key % 10 == 0))
            {
                var customer = _customers.First(_ => _.Key % 10 == 0);
                yield return new Customer(customer.Value.Name, customer.Key);
                _customers.Remove(customer);
                await Task.Delay(500,cancellationToken);
            }
        }

const int TARGET = 80;
var _httpClient = new HttpClient();
var _cancelationTokenSource = new CancellationTokenSource();

using (var response = await _httpClient.GetAsync(
    "https://localhost:7284/customer",
     HttpCompletionOption.ResponseHeadersRead,
     _cancelationTokenSource.Token))
{
    var stream = await response.Content.ReadAsStreamAsync(_cancelationTokenSource.Token);

    var _jsonSerializerSettings = new JsonSerializerSettings();
    var _serializer = Newtonsoft.Json.JsonSerializer.Create(_jsonSerializerSettings);

    using TextReader textReader = new StreamReader(stream);
    using JsonReader jsonReader = new JsonTextReader(textReader);

    await using (stream.ConfigureAwait(false))
    {
        await jsonReader.ReadAsync(_cancelationTokenSource.Token).ConfigureAwait(false);
        while (await jsonReader.ReadAsync(_cancelationTokenSource.Token).ConfigureAwait(false) &&
               jsonReader.TokenType != JsonToken.EndArray)
        {
            Customer customer = _serializer!.Deserialize<Customer>(jsonReader);
            if (customer.Id == TARGET)
            {
                Console.WriteLine(customer.Id + " : " + customer.Name);
                _cancelationTokenSource.Cancel();
                break;
            }
        }
    }
}