add graceful shutdown

Author: nammn

main.go

@@ -197,7 +197,7 @@ func main() {
 			// Force a flush of any pending spans
 			shutdownCtx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
 			defer cancel()
-			if err := tp.ForceFlush(shutdownCtx); err != nil {
+			if err := tp.Shutdown(shutdownCtx); err != nil {
 				log.Errorf("Error flushing spans: %v", err)
 			} else {
 				log.Info("Spans successfully flushed")