code: func (l *Locking) NormFloat64() (v float64) {
  	l.Lock()
  	v = l.R.NormFloat64()
  	l.Unlock()
  	return
  }
docs: // NormFloat64 returns a normally distributed float64 in the range
  // [-math.MaxFloat64, +math.MaxFloat64] with standard normal distribution
  // (mean = 0, stddev = 1) from the source in the context or the shared global
  // source.
  //
  // To produce a different normal distribution, callers can adjust the output
  // using:
  //
  //  sample = NormFloat64(ctx) * desiredStdDev + desiredMean
  //