code: func (si *SI) ToString() string {
  	defer si.mu.Unlock()
  	si.mu.Lock()
  	return si.String()
  }
docs: /*
  Convert to string in a thread safe way.
   Output:
  	uptime		279h6m21s
  	load		0.12 0.04 0.05
  	procs		143
  	ram  total	383752 kB
  	ram  free	254980 kB
  	ram  buffer	7640 kB
  	swap total	887800 kB
  	swap free	879356 kB
  */