Renew SAS token used by Azure Iot Hub DeviceClient - azure

Question

How to renew SASToken which is generated and valid for one hour given the code below?
I cannot see any method to renew the SAS token.
public class IotHubService
{
Microsoft.Azure.Devices.Client.DeviceClient _deviceClient;
public void InitDeviceClient()
{
var sasToken = CreateOrRenewIotSasToken();
_deviceClient = DeviceClient.Create(_iotHubEndpoint,
new DeviceAuthenticationWithToken(deviceId, sasToken),
TransportType.Mqtt_WebSocket_Only);
_deviceClient.SetRetryPolicy(retryPolicy);
// Set handlers and callbacks
_deviceClient.SetConnectionStatusChangesHandler(ConnectionStatusChanged);
_iotHubCancellationTokenSource = new CancellationTokenSource();
await _deviceClient.OpenAsync(_iotHubCancellationTokenSource.Token);
}
public async Task<string> CreateOrRenewIotSasToken()
{
var iotHubEndpoint = AppConfig.IotHubEndpoint;
var deviceId = await GetDeviceIdAsync();
var sharedKey = _appConfigProvider.AppConfig.SharedKey;
var symmetricKey = _symmetricKeyProvider.GenerateSymmetricKey(deviceId, sharedKey);
_iotSasToken = GenerateSasToken(iotHubEndpoint, symmetricKey, null,3600);
return _iotSasToken;
}
public string GenerateSasToken(string resourceUri, string key, string policyName, int expiryInSeconds)
{
var fromEpochStart = _dateTimeProvider.GetUtcDateTime() - new DateTime(1970, 1, 1);
var expiry = $"{fromEpochStart.TotalSeconds + expiryInSeconds}";
var stringToSign = WebUtility.UrlEncode(resourceUri) + "\n" + expiry;
var hmac = new HMACSHA256(Convert.FromBase64String(key));
var signature = Convert.ToBase64String(hmac.ComputeHash(Encoding.UTF8.GetBytes(stringToSign)));
var token = String.Format(CultureInfo.InvariantCulture, "SharedAccessSignature sr={0}&sig={1}&se={2}", WebUtility.UrlEncode(resourceUri), WebUtility.UrlEncode(signature), expiry);
if (!String.IsNullOrEmpty(policyName))
{
token += "&skn=" + policyName;
}
return token;
}
}
Microsoft.Azure.Devices.Client: 1.21.0