Flush metric events prior to shutdown in OTLP example (#1678)

* Flush metric events prior to shutdown in OTLP example

* Add changes to changelog

CHANGELOG.md

@@ -38,6 +38,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - `SamplingResult.TraceState` is correctly propagated to a newly created
   span's `SpanContext`. (#1655)
 - Jaeger Exporter: Ensure mapping between OTEL and Jaeger span data complies with the specification. (#1626)
+- The `otel-collector` example now correctly flushes metric events prior to shutting down the exporter. (#1678)
 
 ## [0.18.0] - 2020-03-03
 

example/otel-collector/main.go

@@ -90,11 +90,11 @@ func initProvider() func() {
 	handleErr(cont.Start(context.Background()), "failed to start controller")
 
 	return func() {
-		// Shutdown will flush any remaining spans.
-		handleErr(tracerProvider.Shutdown(ctx), "failed to shutdown TracerProvider")
-
 		// Push any last metric events to the exporter.
 		handleErr(cont.Stop(context.Background()), "failed to stop controller")
+
+		// Shutdown will flush any remaining spans and shut down the exporter.
+		handleErr(tracerProvider.Shutdown(ctx), "failed to shutdown TracerProvider")
 	}
 }