fix: Memory leak (panjf2000#114)

Fixes panjf2000#113

Avoid memory leak (panjf2000#107)

Improve the unlimited pool

Updates panjf2000#90

Renew go version

Fix a bug that doesn't release lock (panjf2000#79)

Update info and fix typos

Optimize loop queue of workers

Optimize the logic when putting worker back to sync.Pool

Add doc.go

Refine the logic of sync.Pool