private async Task<string> GetAccessTokenAsync()
        {
            string _accessToken = null;
            DateTime _accessTokenExpiry = DateTime.MinValue;
            if (_accessToken != null && DateTime.UtcNow < _accessTokenExpiry)
            {
                return _accessToken;
            }

            using (HttpClient client = new HttpClient())
            {
                var discoveryRequest = new DiscoveryDocumentRequest
                {
                    Address = "https://staging.osipi.com/identity",
                    Policy = new DiscoveryPolicy
                    {
                        Authority = "https://identity.osisoft.com",
                        ValidateEndpoints = false,
                        ValidateIssuerName = false
                    }
                };

                var discoveryResponse = await client.GetDiscoveryDocumentAsync(discoveryRequest);

                if (discoveryResponse.IsError)
                    throw new InvalidOperationException(discoveryResponse.Error);

                var clientCredentialsTokenRequest = new ClientCredentialsTokenRequest
                {
                    Address = discoveryResponse.TokenEndpoint,
                    ClientId = "cf8611cc-d754-4a42-802c-b4500506a718",
                    ClientSecret = "LyzBLtHl56LOskMfke9l74dk5Y4Cts4kJVxQgWSeRSQ=",
                    Scope = "ocsapi"
                };

                DateTime now = DateTime.UtcNow;

                var tokenResponse = await client.RequestClientCredentialsTokenAsync(clientCredentialsTokenRequest);

                if (discoveryResponse.IsError)
                    throw new InvalidOperationException(tokenResponse.Error);

                if (string.IsNullOrEmpty(tokenResponse.AccessToken))
                    throw new InvalidOperationException("Failed to acquire Access Token");

                _accessToken = tokenResponse.AccessToken;

                // Add a buffer of 30 seconds to the expiration delta.
                _accessTokenExpiry = now.AddSeconds(tokenResponse.ExpiresIn - 30);

                return _accessToken;
            }
        }