v2.2.1: Merge pull request #25 from singchia/fix/close-post-risk

#25

v2.2.0: Merge pull request #22 from singchia/bench/resource

1. GC optimize
2. Resource optimize

v2.1.0: Merge pull request #18 from singchia/feat/readme_optimize

feat: optimized readme

A bugfix version.

#16 and #15

An Add always succeed after Close.

Merge pull request #14 from singchia/feat/add_must_succeed

feat: An Add returns succeed after timer Close

New interface and lockfree design timer.

New interface design.
Keep main routine lockfree.
Add more features.

A release for the old version interfaces.

A long term support version.

v0.0.7

fix: goroutine leak after Close

v0.0.3

feat: renew scheduler

The very first version.

v0.0.1

renew deps