add info regarding heartbeat workaround

Author: mrbullwinkle

articles/azure-monitor/app/worker-service.md

@@ -2,7 +2,7 @@
 title: Application Insights for Worker Service apps (non-HTTP apps)
 description: Monitoring .NET Core/.NET Framework non-HTTP apps with Azure Monitor Application Insights.
 ms.topic: conceptual
-ms.date: 12/16/2019
+ms.date: 05/11/2020
 
 ---
 
@@ -422,7 +422,8 @@ The following automatic-collection modules are enabled by default. These modules
 * `DependencyTrackingTelemetryModule`
 * `PerformanceCollectorModule`
 * `QuickPulseTelemetryModule`
-* `AppServicesHeartbeatTelemetryModule`
+* `AppServicesHeartbeatTelemetryModule` - (There is currently an issue involving this telemetry module. For a temporary workaround see [GitHub Issue 1689](https://github.com/microsoft/ApplicationInsights-dotnet/issues/1689
+).)
 * `AzureInstanceMetadataTelemetryModule`
 
 To configure any default `TelemetryModule`, use the extension method `ConfigureTelemetryModule<T>` on `IServiceCollection`, as shown in the following example.