NewLockedRandGen creates a new instance of LockedRanGen.

RandBytes returns a byte slice of the given length with random data.

WeightedChoice takes a slice of positive weights, and returns a random index from [0, len(weights)) with probability of index i being proportional to weight i.

LockedRandGen wrapper on top of math/rand that leverage locking when generating random number and avoid concurrency issue between go-routines sharing the generator.