An exception occurred during a WebClient request

Thanks in advance. I am getting error "An exception occurred during a WebClient request" on my .net core console application when I am trying to call web api, My code is as below.

public string Post(string url, SyncRequest request)
{
try
{
var settings = ReadConfigFile();
using (WebClient client = new WebClient())
{
string json = JsonConvert.SerializeObject(request);
Uri apiUrl = new Uri($"{settings.Api.DataSyncUrl.Replace("\"", string.Empty).Trim()}/{url}");
client.Headers["Content-type"] = "application/json";
client.Encoding = Encoding.UTF8;
return client.UploadString(apiUrl, json);
}
}
catch (Exception ex)
{
logger.Error($"Error in POST request for URL : { url } , { ex.Message }");
return ex.Message;
}
}

public static AppSettings ReadConfigFile()
{
try
{
var fileName = Directory.GetCurrentDirectory() + "/\\appsettings.json";
AppSettings config = null;
using (StreamReader file = File.OpenText(fileName))
{
string jsonString = file.ReadToEnd();
config = JsonConvert.DeserializeObject<AppSettings>(jsonString);
}
return config;
}
catch (Exception ex)
{
logger.Error($"Error in reading json file , { ex.StackTrace }");
return null;
}
}