code: func (nc *Conn) processPingTimer() {
  	nc.mu.Lock()
  
  	if nc.status != CONNECTED {
  		nc.mu.Unlock()
  		return
  	}
  
  	// Check for violation
  	nc.pout++
  	if nc.pout > nc.Opts.MaxPingsOut {
  		nc.mu.Unlock()
  		nc.processOpErr(ErrStaleConnection)
  		return
  	}
  
  	nc.sendPing(nil)
  	nc.ptmr.Reset(nc.Opts.PingInterval)
  	nc.mu.Unlock()
  }
docs: // This will fire periodically and send a client origin
  // ping to the server. Will also check that we have received
  // responses from the server.