Merge pull request #4 from golib/feature/pkg-rand

What: bomb to v1.3.0

Merge pull request #3 from golib/feature/go-mod

What: bomb to v1.2.0

Merge pull request #2 from golib/master-exp-rand

What: refactor random weighted alg with exp/rand

Merge pull request #1 from golib/master-issue-6

What: fix rand.Intn concurrency issues