code: func (c *nameCoordinator) Has(name string) bool {
  	hostname, _, err := net.SplitHostPort(name)
  	if err != nil {
  		hostname = name
  	}
  	c.mu.RLock()
  	_, ok := c.names[strings.ToLower(hostname)]
  	c.mu.RUnlock()
  	return ok
  }
docs: // Has returns true if c has name. It is safe for concurrent use.