test(spanner): fix race when accessing trace spans (#10186)

* test(spanner): fix race when accessing trace spans

* fix go vet

* fix build

* return span data itself

* fix go vet

* fix vet

* revert changes

* revert other module changes, they will be done after cloud.google.com/go release

---------

Co-authored-by: rahul2393 <irahul@google.com>
Co-authored-by: rahul yadav <rahulyadavsep92@gmail.com>

internal/testutil/trace.go

@@ -27,7 +27,7 @@ import (
 // TestExporter is a test utility exporter. It should be created with NewtestExporter.
 type TestExporter struct {
 	mu    sync.Mutex
-	Spans []*trace.SpanData
+	spans []*trace.SpanData
 
 	Stats chan *view.Data
 	Views []*view.View
@@ -56,7 +56,16 @@ func NewTestExporter(views ...*view.View) *TestExporter {
 func (te *TestExporter) ExportSpan(s *trace.SpanData) {
 	te.mu.Lock()
 	defer te.mu.Unlock()
-	te.Spans = append(te.Spans, s)
+	te.spans = append(te.spans, s)
+}
+
+// Spans returns the exported spans.
+func (te *TestExporter) Spans() []*trace.SpanData {
+	te.mu.Lock()
+	defer te.mu.Unlock()
+	spans := make([]*trace.SpanData, len(te.spans))
+	copy(spans, te.spans)
+	return spans
 }
 
 // ExportView exports a view.

internal/trace/trace_test.go

@@ -63,7 +63,7 @@ func TestStartSpan_OpenCensus(t *testing.T) {
 	if IsOpenTelemetryTracingEnabled() {
 		t.Errorf("got true, want false")
 	}
-	spans := te.Spans
+	spans := te.Spans()
 	if len(spans) != 1 {
 		t.Fatalf("got %d, want 1", len(spans))
 	}