code: func isSecretExpired(secret *v1.Secret) bool {
  	expiration := getSecretString(secret, bootstrapapi.BootstrapTokenExpirationKey)
  	if len(expiration) > 0 {
  		expTime, err2 := time.Parse(time.RFC3339, expiration)
  		if err2 != nil {
  			klog.V(3).Infof("Unparseable expiration time (%s) in %s/%s Secret: %v. Treating as expired.",
  				expiration, secret.Namespace, secret.Name, err2)
  			return true
  		}
  		if time.Now().After(expTime) {
  			klog.V(3).Infof("Expired bootstrap token in %s/%s Secret: %v",
  				secret.Namespace, secret.Name, expiration)
  			return true
  		}
  	}
  	return false
  }
docs: // isSecretExpired returns true if the Secret is expired.