logging

Overview ¶

Package logging constructs the *slog.Logger a process writes through, from a configuration that takes part in the layered load.

The package exports:

• Config, the logger's configuration, loaded with the config package
• Env and NewEnv, the environment override names Config reads
• Level and its constants LevelDebug, LevelInfo, LevelWarn, and LevelError, the minimum level the logger emits
• Format and its constants FormatText and FormatJSON, the handler the logger writes through
• New, which constructs the logger

Configuration ¶

Config holds a Level and a Format and implements the config package's Merge and Finalize contract, so it loads as part of an application's configuration rather than on its own. Finalize runs, in order:

• composes its override names from the prefix it receives with NewEnv, recording them on Env
• normalizes (trims and lower-cases)
• applies defaults (info, text)
• reads the overrides
• normalizes again
• validates

A value from a file or a shell therefore validates identically in any casing, and a blank or whitespace-only value takes the default. An empty prefix composes no names, disabling the overrides.

Construction ¶

New returns a logger writing to the caller's io.Writer, with a JSON handler for FormatJSON and a text handler otherwise. Finalize is the validation point: New returns no error, and a Config that skipped Finalize yields an info-level logger.

Record times ¶

Both handlers write each record's time in time.UTC, whatever time.Local is, so it ends in "Z" in either format. Only the record's own time is converted: a time.Time the caller passes as an attribute is written as the caller built it.