// error.go
func isTimeoutError(err error) (isTimeout bool, hasTimeoutFlag bool) {
	// Check for timeoutError interface (works with wrapped errors)
	var te timeoutError
	if errors.As(err, &te) {
		return true, te.Timeout()
	}

	// Check for net.Error specifically (common case for network timeouts)
	var netErr net.Error
	if errors.As(err, &netErr) {
		return true, netErr.Timeout()
	}

	return false, false
}

func shouldRetry(err error, retryTimeout bool) bool {
	...

	// Check for timeout errors (works with wrapped errors)
	if isTimeout, hasTimeoutFlag := isTimeoutError(err); isTimeout {
		if hasTimeoutFlag {
			return retryTimeout
		}
		return true
	}

//osscluster.go
func (c *ClusterClient) process(ctx context.Context, cmd Cmder) error {
...
if shouldRetry(lastErr, cmd.readTimeout() == nil) && !cmd.NoRetry() {
			// First retry the same node.
			if attempt == 0 {
				continue
			}

			// Second try another node.
			node.MarkAsFailing()
			node = nil
			continue
		}
...
}

func (e *OpError) Timeout() bool {
	if ne, ok := e.Err.(*os.SyscallError); ok {
		t, ok := ne.Err.(timeout)
		return ok && t.Timeout()
	}
	t, ok := e.Err.(timeout)
	return ok && t.Timeout()
}

// errors.go

// isDialError reports whether err is a connection-establishment error,
// meaning the TCP dial failed before any data was sent to the server.
func isDialError(err error) bool {
	var opErr *net.OpError
	return errors.As(err, &opErr) && opErr.Op == "dial"
}

func shouldRetry(err error, retryTimeout bool) bool {
	...

	// Check for timeout errors (works with wrapped errors)
	if isTimeout, hasTimeoutFlag := isTimeoutError(err); isTimeout {
		if hasTimeoutFlag {
			// A dial error means the TCP connection was never established and the
			// command was never sent to the server, so retry is always safe
			if isDialError(err) {
				return true
			}
			return retryTimeout
		}
		return true
        ...
}