You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: gocdk_pub_sub.go
    path of file: ./repos/seaweedfs/weed/notification/gocdk_pub_sub
    
    the code of the file until where you have to start completion: //go:build gocdk
// +build gocdk

// Package gocdk_pub_sub supports the Go CDK (Cloud Development Kit) PubSub API,
// which in turn supports many providers, including Amazon SNS/SQS, Azure Service Bus,
// Google Cloud PubSub, and RabbitMQ.
//
// In the config, select a provider and topic using a URL. See

    
func (k *GoCDKPubSub) Initialize(configuration util.Configuration, prefix string) error {
	k.topicURL = configuration.GetString(prefix + "topic_url")
	glog.V(0).Infof("notification.gocdk_pub_sub.topic_url: %v", k.topicURL)
	topic, err := pubsub.OpenTopic(context.Background(), k.topicURL)
	if err != nil {
		glog.Fatalf("Failed to open topic: %v", err)
	}
	k.setTopic(topic)
	return nil
}