code: func NewSimpleLogger3(out io.Writer, prefix string, flag int, l core.LogLevel) *SimpleLogger {
  	return &SimpleLogger{
  		DEBUG: log.New(out, fmt.Sprintf("%s [debug] ", prefix), flag),
  		ERR:   log.New(out, fmt.Sprintf("%s [error] ", prefix), flag),
  		INFO:  log.New(out, fmt.Sprintf("%s [info]  ", prefix), flag),
  		WARN:  log.New(out, fmt.Sprintf("%s [warn]  ", prefix), flag),
  		level: l,
  	}
  }
docs: // NewSimpleLogger3 let you customrize your logger prefix and flag and logLevel