fix(sec): upgrade gopkg.in/yaml.v2 to 2.2.8

[fynntang]

What happened？

There are 1 security vulnerabilities found in gopkg.in/yaml.v2 v2.0.0-20170812160011-eb3733d160e7

• CVE-2019-11254

What did I do？

Upgrade gopkg.in/yaml.v2 from v2.0.0-20170812160011-eb3733d160e7 to 2.2.8 for vulnerability fix

What did you expect to happen？

Ideally, no insecure libs should be used.

The specification of the pull request

PR Specification from OSCS