event.go

	for _, event := range events {
		if event.Type == linebot.EventTypeMessage {
			switch message := event.Message.(type) {
			.......
      case *linebot.VideoMessage:
              //Get Video binary from LINE server based on message ID.
              content, err := bot.GetMessageContent(message.ID).Do()
              if err != nil {
                log.Println("Got GetMessageContent err:", err)
              }
              defer content.Content.Close()