only for practice. Gen http client api call from protobuf.
rebuild and install bin
$ go install
test if works.
$ protoc --go-http-client_out=. --go-http-client_opt="paths=source_relative" example/*.proto
add opts from command.
$ protoc --go-http-client_out=. --go-http-client_opt=paths=source_relative,test=from_command example/*.proto