code: func (l *Logger) Rotate() error {
  	l.mu.Lock()
  	defer l.mu.Unlock()
  	return l.rotate()
  }
docs: // Rotate causes Logger to close the existing log file and immediately create a
  // new one.  This is a helper function for applications that want to initiate
  // rotations outside of the normal rotation rules, such as in response to
  // SIGHUP.  After rotating, this initiates compression and removal of old log
  // files according to the configuration.