Go errors don't carry stack traces. How do you get stack information when you need it?

The standard library leaves stacks out of errors on purpose: capturing them costs time, and well-written wrap messages usually give enough context. When you do need one:

• runtime/debug.Stack() / debug.PrintStack(): the current goroutine's stack, typically captured in a recover handler.
• runtime.Callers + runtime.CallersFrames: record program counters cheaply when the error is created, and turn them into symbols only when printing.
• GOTRACEBACK=all|system|crash controls how much a crash prints (crash also produces a core dump). debug.SetTraceback sets it from code.
• Third-party packages (pkg/errors, which is archived, or cockroachdb/errors) and log/slog with the source option.

type stackErr struct {
	err error
	pcs []uintptr
}

func (e *stackErr) Error() string { return e.err.Error() }
func (e *stackErr) Unwrap() error { return e.err }

func WithStack(err error) error {
	pcs := make([]uintptr, 32)
	n := runtime.Callers(2, pcs) // skip Callers and WithStack
	return &stackErr{err, pcs[:n]}
}

func (e *stackErr) Stack() string {
	var b strings.Builder
	frames := runtime.CallersFrames(e.pcs)
	for {
		f, more := frames.Next()
		fmt.Fprintf(&b, "%s\n\t%s:%d\n", f.Function, f.File, f.Line)
		if !more {
			return b.String()
		}
	}
}

Capture a stack once, at the lowest point where the error enters your code, not at every layer.