create a client with Tls12 support

request-sample.cs

namespace MyApp.ApiClient;

public class HttpClientApiService(HttpClient httpClient)
{
    public async Task<ItemDto?> GetItemAsync(int itemId, CancellationToken cancellationToken = default)
    {
       // get item from /api/items/{itemId} sending accept: application/json
         var request = new HttpRequestMessage(HttpMethod.Get, $"/api/items/{itemId}");
        request.Headers.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));
        var response = await httpClient.SendAsync(request, cancellationToken);
        response.EnsureSuccessStatusCode();
        var content = await response.Content.ReadAsStringAsync(cancellationToken);
        var item = System.Text.Json.JsonSerializer.Deserialize<ItemDto>(content, new System.Text.Json.JsonSerializerOptions
        {
            PropertyNameCaseInsensitive = true
        });

        return item;
    }
}

public record ItemDto(int Id, string Name);

sample-with-dependency-injection.cs

services.AddSingleton(sp =>
{
    // Assuming you have configs as a service
    var config = sp.GetRequiredService<IAppConfiguration>();

    var handler = new SocketsHttpHandler
    {
        AllowAutoRedirect = true,
        AutomaticDecompression = System.Net.DecompressionMethods.All,
        SslOptions = { EnabledSslProtocols = System.Security.Authentication.SslProtocols.Tls12 | System.Security.Authentication.SslProtocols.Tls13 },
        ConnectTimeout = config.HttpConnectTimeout
    };

    var client = new HttpClient(handler);
    client.DefaultRequestHeaders.Accept.ParseAdd("image/*;q=0.8,*/*;q=0.5");
    client.DefaultRequestHeaders.AcceptLanguage.ParseAdd("en-US,en;q=0.9");
    client.DefaultRequestHeaders.UserAgent.ParseAdd("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 Chrome/120.0.0.0 Safari/537.36");
    client.Timeout = config.HttpTotalTimeout;
    return client;
});

sample.cs

var handler = new SocketsHttpHandler
{
    AllowAutoRedirect = true,
    AutomaticDecompression = System.Net.DecompressionMethods.All,
    SslOptions = { EnabledSslProtocols = System.Security.Authentication.SslProtocols.Tls12 | System.Security.Authentication.SslProtocols.Tls13 },
    ConnectTimeout = TimeSpan.FromSeconds(15)
};

var client = new HttpClient(handler);
client.DefaultRequestHeaders.Accept.ParseAdd("image/*;q=0.8,*/*;q=0.5");
client.DefaultRequestHeaders.AcceptLanguage.ParseAdd("en-US,en;q=0.9");
client.DefaultRequestHeaders.UserAgent.ParseAdd("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 Chrome/120.0.0.0 Safari/537.36");
client.Timeout = TimeSpan.FromSeconds(60);
return client;