Another implementation of logr interface with addition of systemd specific prefixes (severity levels). This logger is meant for apps/services that are started via systemd and want to send their logs to the system journal.
logr.Info and logr.Error messages are prefixed by SD_INFO and SD_ERR respectively and therefor should be easy to distinguish and filter with journalctl command.
// from systemd/sd-daemon.h
#define SD_EMERG "<0>" /* system is unusable */
#define SD_ALERT "<1>" /* action must be taken immediately */
#define SD_CRIT "<2>" /* critical conditions */
#define SD_ERR "<3>" /* error conditions */
#define SD_WARNING "<4>" /* warning conditions */
#define SD_NOTICE "<5>" /* normal but significant condition */
#define SD_INFO "<6>" /* informational */
#define SD_DEBUG "<7>" /* debug-level messages */