code: func (a *Agent) Join(addrs []string, replay bool) (n int, err error) {
  	a.logger.Printf("[INFO] agent: joining: %v replay: %v", addrs, replay)
  	ignoreOld := !replay
  	n, err = a.serf.Join(addrs, ignoreOld)
  	if n > 0 {
  		a.logger.Printf("[INFO] agent: joined: %d nodes", n)
  	}
  	if err != nil {
  		a.logger.Printf("[WARN] agent: error joining: %v", err)
  	}
  	return
  }
docs: // Join asks the Serf instance to join. See the Serf.Join function.