code: func (cs *clientStore) removeClientHB(c *client) {
  	if c == nil {
  		return
  	}
  	c.Lock()
  	if c.hbt != nil {
  		c.hbt.Stop()
  		c.hbt = nil
  	}
  	c.Unlock()
  }
docs: // removeClientHB will stop and remove the client's heartbeat timer, if
  // present.