GKE中のGolangアプリケーションからCloud Pub/Subを使ってデータ連携を行う

package main

import (
    "context"
    "encoding/json"
    "flag"
    "fmt"
    "log"

    "cloud.google.com/go/pubsub"
)

var (
    topicID   = flag.String("topic-id", "sample-topic", "Specify topic to publish message")
    projectID = flag.String("project-id", "sample-project", "Specify GCP project you want to work on")
)

func main() {
    flag.Parse()

    err := publishMsg(*projectID, *topicID,
        map[string]string{
            "user":    "Hashimoto",
            "message": "more than happy",
            "status":  "bonus day!",
        },
        nil)
    if err != nil {
        log.Fatalf("Failed to create client: %v", err)
    }
}

func publishMsg(projectID, topicID string, attr map[string]string, msg map[string]string) error {
    // projectID := "my-project-id"
    // topicID := "my-topic"
    // msg := message data publish to topic
    // attr := attribute of message
    ctx := context.Background()
    client, err := pubsub.NewClient(ctx, projectID)
    if err != nil {
        return fmt.Errorf("pubsub.NewClient: %v", err)
    }

    bMsg, err := json.Marshal(msg)
    if err != nil {
        return fmt.Errorf("Input msg error : %v", err)
    }

    t := client.Topic(topicID)
    result := t.Publish(ctx, &pubsub.Message{
        Data:       bMsg,
        Attributes: attr,
    })

    // ID is returned for the published message.
    id, err := result.Get(ctx)
    if err != nil {
        return fmt.Errorf("Get: %v", err)
    }
    fmt.Printf("Published message with custom attributes; msg ID: %v\n", id)

    return nil
}