Setup GitHub Workflow for auto `go tidy` (#3512)
Setup GitHub Workflow for auto `go tidy` (#3512)

Setup GitHub Workflow for auto `go tidy`, when
- 'go.mod'
- 'go.sum'
- '.github/workflows/go.tidy.yml'
has been touched.

Signed-off-by: Yong Tang <765086fe2e0c1f980161f127fec596800f327f62@outlook.com>
yongtang/coredns,chrisohaver/coredns,coredns/coredns,johnbelamaric/coredns,miekg/coredns,miekg/coredns,johnbelamaric/coredns