code: func SeedMathRand() {
  	once.Do(func() {
  		n, err := crand.Int(crand.Reader, big.NewInt(math.MaxInt64))
  		if err != nil {
  			rand.Seed(time.Now().UTC().UnixNano())
  			return
  		}
  		rand.Seed(n.Int64())
  		SeededSecurely = true
  	})
  }
docs: // SeedMathRand provides weak, but guaranteed seeding, which is better than
  // running with Go's default seed of 1.  A call to SeedMathRand() is expected
  // to be called via init(), but never a second time.