code: func (l *Logger) SetFlags(flag int) {
  	l.Logger.SetFlags(flag)
  
  	// Only proceed if we've actually got a prefix
  	if l.Prefix() == "" {
  		return
  	}
  
  	const clnSpc = ": "
  	if flag&(log.Lshortfile|log.Llongfile) != 0 {
  		l.SetPrefix(strings.TrimSuffix(l.Prefix(), clnSpc))
  	} else {
  		l.SetPrefix(l.Prefix() + clnSpc)
  	}
  }
docs: // SetFlags is a wrapper around log.SetFlags that adds and removes, ": " to and
  // from a prefix. This is needed because ": " is only added by golang's log
  // package if either of the Lshortfile or Llongfile flags are set.