code: func fallbackNewRandom(random *rand.Rand) *rand.Rand {
  	// Return the passed in value if it's already not null
  	if nil != random {
  		return random
  	}
  
  	seed := time.Now().UnixNano()
  
  	return rand.New(rand.NewSource(seed))
  }
docs: // fallbackNewRandom returns the passed in random instance if it's not nil,
  // and otherwise returns a new random instance seeded with the current time.