fetch messages from Gmail

main.go

func getLastMessageId(srv *gmail.Service) string {
	r, err := srv.Users.Messages.List(user).MaxResults(100).Q("to:testuser+garminlivetrack@gmail.com is:unread").Do()
	if err != nil {
		log.Fatalf("Unable to retrieve messages: %v", err)
	}
	if len(r.Messages) == 0 {
		fmt.Println("No messages found.")
		os.Exit(1)
	}
	return r.Messages[len(r.Messages)-1].Id
}

func getLastMessageData(srv *gmail.Service, lastMessageId string) string {
	r, err := srv.Users.Messages.Get(user, lastMessageId).Do()
	if err != nil {
		log.Fatalf("Unable to retrieve message: %v", err)
	}
	if len(r.Id) == 0 {
		fmt.Println("No message data found.")
		return ""
	}
	return r.Payload.Body.Data
}

func markAsRead(srv *gmail.Service, lastMessageId string) {
	var labels []string
	labels = append(labels, "UNREAD")
	_, err := srv.Users.Messages.Modify(user, lastMessageId, &gmail.ModifyMessageRequest{RemoveLabelIds: labels}).Do()
	if err != nil {
		log.Fatalf("Unable to modify message: %v", err)
	}
}