code: func (h *HandlerT) StartGoTrace(file string) error {
  	h.mu.Lock()
  	defer h.mu.Unlock()
  	if h.traceW != nil {
  		return errors.New("trace already in progress")
  	}
  	f, err := os.Create(expandHome(file))
  	if err != nil {
  		return err
  	}
  	if err := trace.Start(f); err != nil {
  		f.Close()
  		return err
  	}
  	h.traceW = f
  	h.traceFile = file
  	log.Info("Go tracing started", "dump", h.traceFile)
  	return nil
  }
docs: // StartGoTrace turns on tracing, writing to the given file.