[chore][exporter/exporterhelper] Enable goleak test

This enables goleak to run on tests within exporter/exporterhelper.
A known leak needs to be ignored, and we need to explicitly call
shutdown on the queue to make sure no routines are still running
after the test is complete.

exporter/exporterhelper/package_test.go

@@ -0,0 +1,17 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package exporterhelper
+
+import (
+	"testing"
+
+	"go.uber.org/goleak"
+)
+
+// The IgnoreTopFunction call prevents catching the leak generated by opencensus
+// defaultWorker.Start which at this time is part of the package's init call.
+// See https://github.com/open-telemetry/opentelemetry-collector/issues/9165#issuecomment-1874836336 for more context.
+func TestMain(m *testing.M) {
+	goleak.VerifyTestMain(m, goleak.IgnoreTopFunction("go.opencensus.io/stats/view.(*worker).start"))
+}

exporter/exporterhelper/queue_sender_test.go

@@ -328,6 +328,7 @@ func TestQueuedRetryPersistentEnabled_NoDataLossOnShutdown(t *testing.T) {
 
 	// wait for the item to be consumed from the queue
 	replacedReq.checkNumRequests(t, 1)
+	require.NoError(t, be.Shutdown(context.Background()))
 }
 
 func TestQueueSenderNoStartShutdown(t *testing.T) {