1.12.7

Enhancement

• upgrade golang version to 1.9.7.
• add new troubleshooting API for dumping go-routines stack trace.
• replaced runc binary which built from rancher CVE Github repository.
• adjusted default graph driver priority for better usage on CentOS 7.

BUG Fixes

• Fixed FD leak after running wrong command in the exec session.

Others

• rebuild new CI on Github actions.
• make RPM package only on CentOS 7 system.