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slog.Handler.WithGroup

September 8, 2026

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type Handler

type Handler interface {
  …

	// WithGroup returns a new Handler with the given group appended to
	// the receiver's existing groups.
	// The keys of all subsequent attributes, whether added by With or in a
	// Record, should be qualified by the sequence of group names.
	//
	// How this qualification happens is up to the Handler, so long as
	// this Handler's attribute keys differ from those of another Handler
	// with a different sequence of group names.
	//
	// A Handler should treat WithGroup as starting a Group of Attrs that ends
	// at the end of the log event. That is,
	//
	//     logger.WithGroup("s").LogAttrs(ctx, level, msg, slog.Int("a", 1), slog.Int("b", 2))
	//
	// should behave like
	//
	//     logger.LogAttrs(ctx, level, msg, slog.Group("s", slog.Int("a", 1), slog.Int("b", 2)))
	//
	// If the name is empty, WithGroup returns the receiver.
	WithGroup(name string) Handler
}

WithGroup serves the same purpose as WithAttrs, but for groups, which we’ve already discussed from the perspective of logging.

The interesting thing to note here is that WithGroup returns a Handler for which all new Attrs are added to the group. In other words, once WithGroup is called on the Handler, there’s no way to “escape” that group. That might sound limiting, but it’s actually quite powerful for a particular case. It’s this behavior that allows you to define a logger that includes all downstream logs in a group. Useful for component-level grouping.

For a contrived example:

logger := /* default logger */
checkoutLogger := logger.WithGroup("checkout")
processCheckout(checkoutLogger, order)
shippingLogger := logger.WithGroup("shipping")
shipProducts(shippingLogger, order)

In this way, any log calls by processCheckout have their attributes added to the “checkout” group, and any by shipProducts have their attributes added to the “shipping” group.

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