logging.go
func (logger *Logger) Logf(level Level, format string, a ...interface{}) {
	logger.log(level, format, a...)
}
func (logger *Logger) Logf(level Level, format string, a ...interface{}) {
	logger.log(level, format, a...)
}
func ( logger * Logger ) Logf ( level Level , format string , a ... interface { } ) { logger . log ( level , format , a ... ) }
// Logf logs provided message with formatting.
Logf logs provided message with formatting .