code: func DNSResolveCheck(host string, timeout time.Duration) Check {
  	resolver := net.Resolver{}
  	return func() error {
  		ctx, cancel := context.WithTimeout(context.Background(), timeout)
  		defer cancel()
  		addrs, err := resolver.LookupHost(ctx, host)
  		if err != nil {
  			return err
  		}
  		if len(addrs) < 1 {
  			return fmt.Errorf("could not resolve host")
  		}
  		return nil
  	}
  }
docs: // DNSResolveCheck returns a Check that makes sure the provided host can resolve
  // to at least one IP address within the specified timeout.