diff --git a/core/discov/clients.go b/core/discov/clients.go
index c97555da..229abdcc 100644
--- a/core/discov/clients.go
+++ b/core/discov/clients.go
@@ -14,6 +14,7 @@ const (
 
 const timeToLive int64 = 10
 
+// TimeToLive is seconds to live in etcd.
 var TimeToLive = timeToLive
 
 func extract(etcdKey string, index int) (string, bool) {
diff --git a/core/discov/config.go b/core/discov/config.go
index e9da8d10..c4dd53ca 100644
--- a/core/discov/config.go
+++ b/core/discov/config.go
@@ -2,11 +2,13 @@ package discov
 
 import "errors"
 
+// EtcdConf is the config item with the given key on etcd.
 type EtcdConf struct {
 	Hosts []string
 	Key   string
 }
 
+// Validate validates c.
 func (c EtcdConf) Validate() error {
 	if len(c.Hosts) == 0 {
 		return errors.New("empty etcd hosts")
diff --git a/core/discov/publisher.go b/core/discov/publisher.go
index 4b4609db..873cbc32 100644
--- a/core/discov/publisher.go
+++ b/core/discov/publisher.go
@@ -11,8 +11,10 @@ import (
 )
 
 type (
+	// PublisherOption defines the method to customize a Publisher.
 	PublisherOption func(client *Publisher)
 
+	// A Publisher can be used to publish the value to an etcd cluster on the given key.
 	Publisher struct {
 		endpoints  []string
 		key        string
@@ -26,6 +28,10 @@ type (
 	}
 )
 
+// NewPublisher returns a Publisher.
+// endpoints is the hosts of the etcd cluster.
+// key:value are a pair to be published.
+// opts are used to customize the Publisher.
 func NewPublisher(endpoints []string, key, value string, opts ...PublisherOption) *Publisher {
 	publisher := &Publisher{
 		endpoints:  endpoints,
@@ -43,6 +49,7 @@ func NewPublisher(endpoints []string, key, value string, opts ...PublisherOption
 	return publisher
 }
 
+// KeepAlive keeps key:value alive.
 func (p *Publisher) KeepAlive() error {
 	cli, err := internal.GetRegistry().GetConn(p.endpoints)
 	if err != nil {
@@ -61,14 +68,17 @@ func (p *Publisher) KeepAlive() error {
 	return p.keepAliveAsync(cli)
 }
 
+// Pause pauses the renewing of key:value.
 func (p *Publisher) Pause() {
 	p.pauseChan <- lang.Placeholder
 }
 
+// Resume resumes the renewing of key:value.
 func (p *Publisher) Resume() {
 	p.resumeChan <- lang.Placeholder
 }
 
+// Stop stops the renewing and revokes the registration.
 func (p *Publisher) Stop() {
 	p.quit.Close()
 }
@@ -135,6 +145,7 @@ func (p *Publisher) revoke(cli internal.EtcdClient) {
 	}
 }
 
+// WithId customizes a Publisher with the id.
 func WithId(id int64) PublisherOption {
 	return func(publisher *Publisher) {
 		publisher.id = id
diff --git a/core/discov/subscriber.go b/core/discov/subscriber.go
index 94c81bfc..83c97fcb 100644
--- a/core/discov/subscriber.go
+++ b/core/discov/subscriber.go
@@ -13,13 +13,19 @@ type (
 		exclusive bool
 	}
 
+	// SubOption defines the method to customize a Subscriber.
 	SubOption func(opts *subOptions)
 
+	// A Subscriber is used to subscribe the given key on a etcd cluster.
 	Subscriber struct {
 		items *container
 	}
 )
 
+// NewSubscriber returns a Subscriber.
+// endpoints is the hosts of the etcd cluster.
+// key is the key to subscribe.
+// opts are used to customize the Subscriber.
 func NewSubscriber(endpoints []string, key string, opts ...SubOption) (*Subscriber, error) {
 	var subOpts subOptions
 	for _, opt := range opts {
@@ -36,15 +42,17 @@ func NewSubscriber(endpoints []string, key string, opts ...SubOption) (*Subscrib
 	return sub, nil
 }
 
+// AddListener adds listener to s.
 func (s *Subscriber) AddListener(listener func()) {
 	s.items.addListener(listener)
 }
 
+// Values returns all the subscription values.
 func (s *Subscriber) Values() []string {
 	return s.items.getValues()
 }
 
-// exclusive means that key value can only be 1:1,
+// Exclusive means that key value can only be 1:1,
 // which means later added value will remove the keys associated with the same value previously.
 func Exclusive() SubOption {
 	return func(opts *subOptions) {