GithubController - wrong http call without HttpClientFactory

GithubController.cs

[HttpGet("TestGithub/{userName}")]
public async Task<IActionResult> TestGithub(string userName)
{

    var httpClient = new HttpClient
    {
        BaseAddress = new Uri("http://api.github.com/"),
        DefaultRequestHeaders =
        {
            { "Accept", "application/vnd.github.v3+json" },
            { "User-Agent", "HttpClientFactoryExample" }
        }
    };

    var accountInfo = await httpClient.GetStringAsync($"users/{userName}");

    return Ok(accountInfo);
}