Debugf calls global logger.Debugf.

Errorf calls global logger.Errorf.

Fatalf calls global logger.Fatalf.

Infof calls global logger.Infof.

SetLevel set loglevel that should output logs.

Span create Custom Span of Provider's Tracer.

Warnf calls global logger.Warnf.

WithCaller returns Logger that set specified runtime.Caller number.

WithoutCaller returns Logger that never logging source location.

CloseFunc must be called at the end of process.

Level - Severity levels.