code: func debugStackPrinter(out io.Writer) {
  	c := make(chan os.Signal, 1)
  	signal.Notify(c, syscall.SIGUSR2)
  	for range c {
  		pprof.Lookup("goroutine").WriteTo(out, 1)
  	}
  }
docs: // print a full goroutine stack trace to the log fd on SIGUSR2