code: func (c *CheckTCP) check() {
  	var currentStatus string
  	previousStatus := c.Status
  
  	conn, err := c.dialer.Dial(`tcp`, c.tcp)
  	if err != nil {
  		logrus.Warnf("[health-check] TCP Check is failing => %s", err)
  		currentStatus = BAD
  	} else {
  		logrus.Debugf("[health-check] TCP check on '%v' at '%s' is passing", c.DestinationID, c.tcp)
  		currentStatus = OK
  		conn.Close()
  	}
  
  	if currentStatus != previousStatus {
  		c.Status = currentStatus
  		c.updateCh <- true
  	}
  }
docs: // check is invoked periodically to perform the TCP check