Merge pull request #661 from panjf2000/dev

patch: v2.6.2

Merge pull request #658 from panjf2000/dev

patch: v2.6.1

Merge pull request #651 from panjf2000/dev

minor: v2.6.0

Merge pull request #641 from panjf2000/dev

patch: v2.5.9

Merge pull request #639 from panjf2000/dev

patch: v2.5.8

Merge pull request #625 from panjf2000/dev

patch: v2.5.7

Merge pull request #623 from panjf2000/dev

patch: v2.5.6

Merge pull request #620 from panjf2000/dev

patch: v2.5.5

Merge pull request #617 from panjf2000/dev

patch: v2.5.4

Merge pull request #607 from panjf2000/dev

patch: v2.5.3