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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"}