在Winforms应用程序中使用单例HttpClient时如何避免死锁

我正在开发一个遗留的Windows窗体应用程序，我对http客户端进行了一些更改，我希望将其作为一个单例，以便在整个应用程序中重用。这似乎造成了僵局。

我将粘贴我认为涉及的所有代码：

这是UI被冻结的调用代码，它从不解冻。

private async void lbGroup_SelectedIndexChanged_1(object sender, EventArgs e)
        {
            int groupId = this.lbGroup.SelectedIndex + 1;
            await LoadStores(groupId);

            //The code below freezes the application
            this.lbStore.DataSource = _stores;
            
            this.txtSearch.Enabled = true;
            this.lbStore.Enabled = true;
        }

这是使用httpClient的LoadStores方法：

private async Task LoadStores(int group)
        {
            try
            {
                HttpResponseMessage res = await _httpClient.GetAsync("api/GetStoresByGroup/" + group.ToString());
                res.EnsureSuccessStatusCode();
                if (res.IsSuccessStatusCode)
                {
                    var serializedStores = await res.Content.ReadAsStringAsync();
                    _stores = JsonConvert.DeserializeObject<IEnumerable<Store>>(serializedStores).Select(s => s.StoreName).ToList();
                    res.Content.Dispose();
                }
            }
            catch (Exception ex)
            {
                ErrorLogger.LogError("Installation", $"Error getting stores list: {ex.Message}");
            }
        }

这是Http Singleton类：

public static class HttpClientSingleton
    {
        private static readonly HttpClient _instance;

        static HttpClientSingleton()
        {
            _instance = new HttpClient();
            _instance.BaseAddress = new Uri("https://www.i-city.co.za/");
            _instance.DefaultRequestHeaders.Accept.Clear();
            _instance.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));
        }

        public static HttpClient Instance
        {
            get
            {
                return _instance;
            }
        }
    }

这是初始化HttpClient的表单构造函数：

public partial class frmInstallationHelper : Form
    {
        private static string _configDir;
        private static string _localConfigDir;
        private static int _storeID;
        private static Activation _activation;
        private static HttpClient _httpClient = HttpClientSingleton.Instance;
        private static IEnumerable<string> _stores;
        private static IEnumerable<string> _franchisees;
        private int _smsCounter;

如果我将http请求包装在LoadStores方法内部的using语句中，那么应用程序运行良好，但我不想丢弃http客户端，因为这会破坏将其作为单例的目的。