pkg/logutil/zap_journal.go
func NewJournalWriter(wr io.Writer) (io.Writer, error) {
	return &journalWriter{Writer: wr}, systemd.DialJournal()
}
func NewJournalWriter(wr io.Writer) (io.Writer, error) {
	return &journalWriter{Writer: wr}, systemd.DialJournal()
}
// NewJournalWriter wraps "io.Writer" to redirect log output
// to the local systemd journal. If journald send fails, it fails
// back to writing to the original writer.
// The decode overhead is only <30µs per write.
// Reference: https://github.com/coreos/pkg/blob/master/capnslog/journald_formatter.go