code: func HostQualifies(hostname string) bool {
  	return hostname != "localhost" && // localhost is ineligible
  
  		// hostname must not be empty
  		strings.TrimSpace(hostname) != "" &&
  
  		// must not contain wildcard (*) characters (until CA supports it)
  		!strings.Contains(hostname, "*") &&
  
  		// must not start or end with a dot
  		!strings.HasPrefix(hostname, ".") &&
  		!strings.HasSuffix(hostname, ".") &&
  
  		// cannot be an IP address, see
  		// https://community.letsencrypt.org/t/certificate-for-static-ip/84/2?u=mholt
  		net.ParseIP(hostname) == nil
  }
docs: // HostQualifies returns true if the hostname alone
  // appears eligible for automatic HTTPS. For example,
  // localhost, empty hostname, and IP addresses are
  // not eligible because we cannot obtain certificates
  // for those names.