Debugf prints debug message according to a format.

Errorf prints warning message according to a format.

ErrorWithCallDepth prints err into error log using the given callDepth.

Fatalf prints fatal message according to a format and exits program.

Infof prints info message according to a format.

SetDebug sets output into debug mode if true passed.

SuppressOutput suppresses all output from logs if `suppress` is true used while testing.

NilLogger suppresses all the log messages.