diff --git a/go/master/etcd_store.go b/go/master/etcd_store.go
index ce178370ff90ddef542bc20e675fe5ada0a5d2f5..d8e95056d5d5c7736ba100898797316c4f392293 100644
--- a/go/master/etcd_store.go
+++ b/go/master/etcd_store.go
@@ -29,6 +29,10 @@ type EtcdStore struct {
 
 // NewEtcdStore creates a new EtcdStore.
 func NewEtcdStore(endpoints []string, lockPath, statePath string, ttlSec int) (*EtcdStore, error) {
+	// TODO(helin): gracefully shutdown etcd store. Becuase etcd
+	// store holds a etcd lock, even though the lock will expire
+	// when the lease timeout, we need to implement graceful
+	// shutdown to release the lock.
 	cli, err := clientv3.New(clientv3.Config{
 		Endpoints:   endpoints,
 		DialTimeout: dialTimeout,