go/slog: How to wrap slog's functions and report the correct source line number

go_slog_critical.go

const (
  LevelCritical = slog.Level(12)
)

// Critical is an example of a user-defined logging function that wraps slog.
// The log record contains the source position of the caller of Critical.
func Critical(msg string, args ...any) {
  if !slog.Default().Enabled(context.Background(), LevelCritical) {
    return
  }
  var pcs [1]uintptr
  runtime.Callers(2, pcs[:]) // skip [Callers, Infof]
  r := slog.NewRecord(time.Now(), LevelCritical, msg, pcs[0])
  r.Add(args...)
  _ = slog.Default().Handler().Handle(context.Background(), r)
}