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April 28, 2026

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Sometimes you want to group several key/value attributes together when logging. Maybe different aspects of an error (error_code, error_detail, stacktrace, etc), or different aspects of an HTTP response (bytes_sent, status_code, etc). The log/slog package gives us this!

Groups

Attributes can be collected into groups. A group has a name that is used to qualify the names of its attributes. How this qualification is displayed depends on the handler. TextHandler separates the group and attribute names with a dot. JSONHandler treats each group as a separate JSON object, with the group name as the key.

Use Group to create a Group attribute from a name and a list of key-value pairs:

slog.Group("request",
    "method", r.Method,
    "url", r.URL)

TextHandler would display this group as

request.method=GET request.url=http://example.com

JSONHandler would display it as

"request":{"method":"GET","url":"http://example.com"}
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Related Content

slog.Group

The one Attr constructor not yet covered: func Group func Group(key string, args ...any) Attr Group returns an Attr for a Group Value. The first argument is the key; the remaining arguments are converted to Attrs as in Logger.Log. Use Group to collect several key-value pairs under a single key on a log line, or as the result of LogValue in order to log a single value as multiple Attrs.

The Attr type

Other than logger methods, the slog.Attr type is probably the thing you’ll use the most in your use of the slog package: Types type Attr type Attr struct { Key string Value Value } An Attr is a key-value pair. This type has several type-specific constructors, too, but we’re going to do an abbrevaited look at them, because they’re highly repetitive. func Any func Any(key string, value any) Attr Any returns an Attr for the supplied value.

Backward compatibility

We’ve already discussed when the default log/slog Logger also serves as the default log Logger. But what if you want to send log logs to a log/slog Logger, without using the global defaults? Introducing NewLogLogger! func NewLogLogger func NewLogLogger(h Handler, level Level) *log.Logger NewLogLogger returns a new log.Logger such that each call to its Output method dispatches a Record to the specified handler. The logger acts as a bridge from the older log API to newer structured logging handlers.

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