The official etcd Go client library is far from easy-to-use. I had to
read github.com/coreos/etcd/client and
github.com/coreos/etcd/etcdctl before I can write this higher-level
abstraction of etcd client.
For documentation, please refer to https://godoc.org/github.com/topicai/etcc