How to generate the authorization token by using the Embed Secret Key API

public class Token
{
    public string access_token { get; set; }

    public string token_type { get; set; }

    public string expires_in { get; set; }

    public string email { get; set; }

    public string error { get; set; }

    public string error_description { get; set; }

}

private static string tokenurl = "/reporting/api/site/site1/token";
private static string boldReportsUrl = "https://demo.example.com"; // Provide your Bold Reports URL
private static string username = "user@example.com"; // Provide your Email ID
private static string nonce = Guid.NewGuid().ToString();
private static string timeStamp = DateTimeToUnixTimeStamp(DateTime.UtcNow).ToString();
private static string secretCode = "lettffAEI0FtKDGdrDekEv7WUbHwOwO"; // Provide your embed secret key value from the Bold Reports Report Server Embed Settings.

public static void Main(string[] args)
{
    ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12; // This is required while running the Bold Reports from Azure App Service
    GetToken();
}

public static Token GetToken()
{
    var client = new HttpClient();
    client.BaseAddress = new Uri(boldReportsUrl);
    client.DefaultRequestHeaders.Accept.Clear();
    client.DefaultRequestHeaders.ConnectionClose = true;
    string embedMessage = "embed_nonce=" + nonce + "&user_email=" + username + "&timestamp=" + timeStamp;
    string signature = SignURL(embedMessage.ToLower(), secretCode);

    var content = new FormUrlEncodedContent(new[]
    {
       new KeyValuePair<string, string>("grant_type", "embed_secret"),
       new KeyValuePair<string, string>("username", username),
       new KeyValuePair<string, string>("embed_nonce", nonce),
       new KeyValuePair<string, string>("embed_signature", signature),
       new KeyValuePair<string, string>("timestamp", timeStamp)
    });

    var result = client.PostAsync(tokenurl, content).Result;

    string resultContent = result.Content.ReadAsStringAsync().Result;

    if (JsonConvert.DeserializeObject<Token>(resultContent)?.error == "authorization_failed")
    {
        Console.WriteLine("authorization_failed: " + JsonConvert.DeserializeObject<Token>(resultContent)?.error_description);
        Console.ReadLine();
        Environment.Exit(-1);
    }

    return JsonConvert.DeserializeObject<Token>(resultContent);
}

public static double DateTimeToUnixTimeStamp(DateTime dateTime)
{
    DateTime unixStart = new DateTime(1970, 1, 1, 0, 0, 0, 0, System.DateTimeKind.Utc);
    long unixTimeStampInTicks = (dateTime.ToUniversalTime() - unixStart).Ticks;
    return unixTimeStampInTicks / TimeSpan.TicksPerSecond;
}

public static string SignURL(string embedMessage, string secretcode)
{
    var encoding = new UTF8Encoding();
    var keyBytes = encoding.GetBytes(secretcode);
    var messageBytes = encoding.GetBytes(embedMessage);
    using (var hmacsha1 = new HMACSHA256(keyBytes))
        {
            var hashMessage = hmacsha1.ComputeHash(messageBytes);
            return Convert.ToBase64String(hashMessage);
        }
}