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

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What happened？

There are 1 security vulnerabilities found in gopkg.in/yaml.v2 v2.2.2

• CVE-2019-11254

What did I do？

Upgrade gopkg.in/yaml.v2 from v2.2.2 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