The close of `done` channel may be called many times.
And the handler will be blocked when the log client exists and the
closure func is still not be called.
So use context to resolve those two problems.
* Update protoc binary executable files to v3.13.0
* Write proto files in more standard way
* Make go generate & vprotogen compatible with protoc-gen-gofast
* Regenerate pb.go files according to new proto files
* Clean go.sum by running go mod tidy
* Implement mustEmbedUnimplementedServiceServer for gPRC services
