code: func init() {
  	r := &randReader{}
  	n, err := rand.Read(r.entropy[:])
  	if err != nil || n != len(r.entropy) {
  		panic("not enough entropy to fill fastrand reader at startup")
  	}
  	Reader = r
  }
docs: // init provides the initial entropy for the reader that will seed all numbers
  // coming out of fastrand.