feat(go): decouple gateway publish with async sink

go/vehicle-gateway/cmd/gateway/main.go

@@ -178,6 +178,20 @@ func buildSink(ctx context.Context, logger *slog.Logger) (eventbus.Sink, error)
 		logger.Info("kafka durable spool enabled", "dir", spoolDir, "replay_interval_ms", interval.Milliseconds(), "replay_batch_size", replayBatchSize)
 		out = durable
 	}
+	if envBool("KAFKA_ASYNC_ENABLED", true) {
+		queueSize := envInt("KAFKA_ASYNC_QUEUE_SIZE", 10000)
+		workers := envInt("KAFKA_ASYNC_WORKERS", 1)
+		timeout := time.Duration(envInt("KAFKA_ASYNC_PUBLISH_TIMEOUT_MS", 30000)) * time.Millisecond
+		out = eventbus.NewAsyncSink(out, eventbus.AsyncConfig{
+			QueueSize:        queueSize,
+			Workers:          workers,
+			OperationTimeout: timeout,
+			OnError: func(err error) {
+				logger.Warn("kafka async publish failed", "error", err)
+			},
+		})
+		logger.Info("kafka async publish enabled", "queue_size", queueSize, "workers", workers, "publish_timeout_ms", timeout.Milliseconds())
+	}
 	return out, nil
 }