diff --git a/core/opentelemetry/attributes.go b/core/opentelemetry/attributes.go
index 0c5f5483..45bfd0ea 100644
--- a/core/opentelemetry/attributes.go
+++ b/core/opentelemetry/attributes.go
@@ -3,43 +3,38 @@ package opentelemetry
 import (
 	"go.opentelemetry.io/otel/attribute"
 	semconv "go.opentelemetry.io/otel/semconv/v1.4.0"
-	grpc_codes "google.golang.org/grpc/codes"
+	gcodes "google.golang.org/grpc/codes"
 )
 
 const (
 	// GRPCStatusCodeKey is convention for numeric status code of a gRPC request.
 	GRPCStatusCodeKey = attribute.Key("rpc.grpc.status_code")
-
-	// Name of message transmitted or received.
+	// RPCNameKey is the name of message transmitted or received.
 	RPCNameKey = attribute.Key("name")
-
-	// Type of message transmitted or received.
+	// RPCMessageTypeKey is the type of message transmitted or received.
 	RPCMessageTypeKey = attribute.Key("message.type")
-
-	// Identifier of message transmitted or received.
+	// RPCMessageIDKey is the identifier of message transmitted or received.
 	RPCMessageIDKey = attribute.Key("message.id")
-
-	// The compressed size of the message transmitted or received in bytes.
+	// RPCMessageCompressedSizeKey is the compressed size of the message transmitted or received in bytes.
 	RPCMessageCompressedSizeKey = attribute.Key("message.compressed_size")
-
-	// The uncompressed size of the message transmitted or received in
-	// bytes.
+	// RPCMessageUncompressedSizeKey is the uncompressed size of the message
+	// transmitted or received in bytes.
 	RPCMessageUncompressedSizeKey = attribute.Key("message.uncompressed_size")
 )
 
 // Semantic conventions for common RPC attributes.
 var (
-	// Semantic convention for gRPC as the remoting system.
+	// RPCSystemGRPC is the semantic convention for gRPC as the remoting system.
 	RPCSystemGRPC = semconv.RPCSystemKey.String("grpc")
-
-	// Semantic convention for a message named message.
+	// RPCNameMessage is the semantic convention for a message named message.
 	RPCNameMessage = RPCNameKey.String("message")
-
-	// Semantic conventions for RPC message types.
-	RPCMessageTypeSent     = RPCMessageTypeKey.String("SENT")
+	// RPCMessageTypeSent is the semantic conventions for sent RPC message types.
+	RPCMessageTypeSent = RPCMessageTypeKey.String("SENT")
+	// RPCMessageTypeReceived is the semantic conventions for the received RPC message types.
 	RPCMessageTypeReceived = RPCMessageTypeKey.String("RECEIVED")
 )
 
-func StatusCodeAttr(c grpc_codes.Code) attribute.KeyValue {
+// StatusCodeAttr returns a attribute.KeyValue that represents the give c.
+func StatusCodeAttr(c gcodes.Code) attribute.KeyValue {
 	return GRPCStatusCodeKey.Int64(int64(c))
 }
diff --git a/core/opentelemetry/clientstream.go b/core/opentelemetry/clientstream.go
index a5a01095..408527a6 100644
--- a/core/opentelemetry/clientstream.go
+++ b/core/opentelemetry/clientstream.go
@@ -9,6 +9,13 @@ import (
 	"google.golang.org/protobuf/proto"
 )
 
+const (
+	receiveEndEvent streamEventType = iota
+	errorEvent
+)
+
+var _ = proto.Marshal
+
 type streamEventType int
 
 type streamEvent struct {
@@ -16,11 +23,6 @@ type streamEvent struct {
 	Err  error
 }
 
-const (
-	receiveEndEvent streamEventType = iota
-	errorEvent
-)
-
 type clientStream struct {
 	grpc.ClientStream
 
@@ -33,11 +35,8 @@ type clientStream struct {
 	sentMessageID     int
 }
 
-var _ = proto.Marshal
-
 func (w *clientStream) RecvMsg(m interface{}) error {
 	err := w.ClientStream.RecvMsg(m)
-
 	if err == nil && !w.desc.ServerStreams {
 		w.sendStreamEvent(receiveEndEvent, nil)
 	} else if err == io.EOF {
@@ -54,10 +53,8 @@ func (w *clientStream) RecvMsg(m interface{}) error {
 
 func (w *clientStream) SendMsg(m interface{}) error {
 	err := w.ClientStream.SendMsg(m)
-
 	w.sentMessageID++
 	MessageSent.Event(w.Context(), w.sentMessageID, m)
-
 	if err != nil {
 		w.sendStreamEvent(errorEvent, err)
 	}
@@ -90,6 +87,7 @@ func (w *clientStream) sendStreamEvent(eventType streamEventType, err error) {
 	}
 }
 
+// WrapClientStream wraps s with given ctx and desc.
 func WrapClientStream(ctx context.Context, s grpc.ClientStream, desc *grpc.StreamDesc) *clientStream {
 	events := make(chan streamEvent)
 	eventsDone := make(chan struct{})
diff --git a/core/opentelemetry/config.go b/core/opentelemetry/config.go
index a34d79fc..0d3b2689 100644
--- a/core/opentelemetry/config.go
+++ b/core/opentelemetry/config.go
@@ -1,5 +1,6 @@
 package opentelemetry
 
+// TraceName represents the tracing name.
 const TraceName = "go-zero"
 
 // A Config is a opentelemetry config.
diff --git a/core/opentelemetry/message.go b/core/opentelemetry/message.go
index fa24ae36..1199db50 100644
--- a/core/opentelemetry/message.go
+++ b/core/opentelemetry/message.go
@@ -9,7 +9,9 @@ import (
 )
 
 var (
-	MessageSent     = messageType(RPCMessageTypeSent)
+	// MessageSent is the type of sent messages.
+	MessageSent = messageType(RPCMessageTypeSent)
+	// MessageReceived is the type of received messages.
 	MessageReceived = messageType(RPCMessageTypeReceived)
 )
 
diff --git a/core/opentelemetry/serverstream.go b/core/opentelemetry/serverstream.go
index 7ad5e5b5..8f740a5a 100644
--- a/core/opentelemetry/serverstream.go
+++ b/core/opentelemetry/serverstream.go
@@ -40,6 +40,7 @@ func (w *serverStream) SendMsg(m interface{}) error {
 	return err
 }
 
+// WrapServerStream wraps the given grpc.ServerStream with the given context.
 func WrapServerStream(ctx context.Context, ss grpc.ServerStream) *serverStream {
 	return &serverStream{
 		ServerStream: ss,
diff --git a/core/opentelemetry/tracer.go b/core/opentelemetry/tracer.go
index ea0dfb15..2328f2e9 100644
--- a/core/opentelemetry/tracer.go
+++ b/core/opentelemetry/tracer.go
@@ -36,12 +36,14 @@ func (s *metadataSupplier) Keys() []string {
 	return out
 }
 
+// Inject injects the metadata into ctx.
 func Inject(ctx context.Context, p propagation.TextMapPropagator, metadata *metadata.MD) {
 	p.Inject(ctx, &metadataSupplier{
 		metadata: metadata,
 	})
 }
 
+// Extract extracts the metadata from ctx.
 func Extract(ctx context.Context, p propagation.TextMapPropagator, metadata *metadata.MD) (baggage.Baggage, trace.SpanContext) {
 	ctx = p.Extract(ctx, &metadataSupplier{
 		metadata: metadata,
diff --git a/core/opentelemetry/utils.go b/core/opentelemetry/utils.go
index 56e27af3..79f56782 100644
--- a/core/opentelemetry/utils.go
+++ b/core/opentelemetry/utils.go
@@ -10,14 +10,17 @@ import (
 	"google.golang.org/grpc/peer"
 )
 
+// PeerFromCtx returns the peer from ctx.
 func PeerFromCtx(ctx context.Context) string {
 	p, ok := peer.FromContext(ctx)
 	if !ok {
 		return ""
 	}
+
 	return p.Addr.String()
 }
 
+// SpanInfo returns the span info.
 func SpanInfo(fullMethod, peerAddress string) (string, []attribute.KeyValue) {
 	attrs := []attribute.KeyValue{RPCSystemGRPC}
 	name, mAttrs := ParseFullMethod(fullMethod)
@@ -26,6 +29,7 @@ func SpanInfo(fullMethod, peerAddress string) (string, []attribute.KeyValue) {
 	return name, attrs
 }
 
+// ParseFullMethod returns the method name and attributes.
 func ParseFullMethod(fullMethod string) (string, []attribute.KeyValue) {
 	name := strings.TrimLeft(fullMethod, "/")
 	parts := strings.SplitN(name, "/", 2)
@@ -41,9 +45,11 @@ func ParseFullMethod(fullMethod string) (string, []attribute.KeyValue) {
 	if method := parts[1]; method != "" {
 		attrs = append(attrs, semconv.RPCMethodKey.String(method))
 	}
+
 	return name, attrs
 }
 
+// PeerAttr returns the peer attributes.
 func PeerAttr(addr string) []attribute.KeyValue {
 	host, port, err := net.SplitHostPort(addr)
 	if err != nil {
diff --git a/core/proc/signals.go b/core/proc/signals.go
index 25c75f46..80ef4bdc 100644
--- a/core/proc/signals.go
+++ b/core/proc/signals.go
@@ -51,6 +51,7 @@ func init() {
 	}()
 }
 
+// Done returns the channel that notifies the process quitting.
 func Done() <-chan struct{} {
 	return done
 }
diff --git a/core/trace/constants.go b/core/trace/constants.go
index 332988d9..33be4a19 100644
--- a/core/trace/constants.go
+++ b/core/trace/constants.go
@@ -1,6 +1,7 @@
 package trace
 
 const (
+	// TraceIdKey is the trace id header.
 	TraceIdKey = "X-Trace-ID"
 
 	spanIdKey = "X-Span-ID"
diff --git a/rest/handler/otelhandler.go b/rest/handler/otelhandler.go
index 8872974f..3dc00341 100644
--- a/rest/handler/otelhandler.go
+++ b/rest/handler/otelhandler.go
@@ -10,6 +10,7 @@ import (
 	oteltrace "go.opentelemetry.io/otel/trace"
 )
 
+// OtelHandler return a middleware that process the opentelemetry.
 func OtelHandler(path string) func(http.Handler) http.Handler {
 	return func(next http.Handler) http.Handler {
 		if !opentelemetry.Enabled() {
diff --git a/zrpc/internal/clientinterceptors/opentracinginterceptor.go b/zrpc/internal/clientinterceptors/opentracinginterceptor.go
index 13f1ea63..657b286a 100644
--- a/zrpc/internal/clientinterceptors/opentracinginterceptor.go
+++ b/zrpc/internal/clientinterceptors/opentracinginterceptor.go
@@ -13,9 +13,11 @@ import (
 	"google.golang.org/grpc/status"
 )
 
+// OpenTracingInterceptor returns a grpc.UnaryClientInterceptor for opentelemetry.
 func OpenTracingInterceptor() grpc.UnaryClientInterceptor {
 	propagator := otel.GetTextMapPropagator()
-	return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
+	return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn,
+		invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
 		if !opentelemetry.Enabled() {
 			return invoker(ctx, method, req, reply, cc, opts...)
 		}
@@ -24,13 +26,8 @@ func OpenTracingInterceptor() grpc.UnaryClientInterceptor {
 		metadataCopy := requestMetadata.Copy()
 		tr := otel.Tracer(opentelemetry.TraceName)
 		name, attr := opentelemetry.SpanInfo(method, cc.Target())
-
-		var span trace.Span
-		ctx, span = tr.Start(ctx,
-			name,
-			trace.WithSpanKind(trace.SpanKindClient),
-			trace.WithAttributes(attr...),
-		)
+		ctx, span := tr.Start(ctx, name, trace.WithSpanKind(trace.SpanKindClient),
+			trace.WithAttributes(attr...))
 		defer span.End()
 
 		opentelemetry.Inject(ctx, propagator, &metadataCopy)
@@ -50,30 +47,23 @@ func OpenTracingInterceptor() grpc.UnaryClientInterceptor {
 	}
 }
 
+// StreamOpenTracingInterceptor returns a grpc.StreamClientInterceptor for opentelemetry.
 func StreamOpenTracingInterceptor() grpc.StreamClientInterceptor {
 	propagator := otel.GetTextMapPropagator()
-	return func(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
+	return func(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string,
+		streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
 		if !opentelemetry.Enabled() {
 			return streamer(ctx, desc, cc, method, opts...)
 		}
 
 		requestMetadata, _ := metadata.FromOutgoingContext(ctx)
 		metadataCopy := requestMetadata.Copy()
-
 		tr := otel.Tracer(opentelemetry.TraceName)
-
 		name, attr := opentelemetry.SpanInfo(method, cc.Target())
-		var span trace.Span
-		ctx, span = tr.Start(
-			ctx,
-			name,
-			trace.WithSpanKind(trace.SpanKindClient),
-			trace.WithAttributes(attr...),
-		)
-
+		ctx, span := tr.Start(ctx, name, trace.WithSpanKind(trace.SpanKindClient),
+			trace.WithAttributes(attr...))
 		opentelemetry.Inject(ctx, propagator, &metadataCopy)
 		ctx = metadata.NewOutgoingContext(ctx, metadataCopy)
-
 		s, err := streamer(ctx, desc, cc, method, opts...)
 		if err != nil {
 			grpcStatus, _ := status.FromError(err)
@@ -82,12 +72,11 @@ func StreamOpenTracingInterceptor() grpc.StreamClientInterceptor {
 			span.End()
 			return s, err
 		}
+
 		stream := opentelemetry.WrapClientStream(ctx, s, desc)
 
 		go func() {
-			err := <-stream.Finished
-
-			if err != nil {
+			if err := <-stream.Finished; err != nil {
 				s, _ := status.FromError(err)
 				span.SetStatus(codes.Error, s.Message())
 				span.SetAttributes(opentelemetry.StatusCodeAttr(s.Code()))
diff --git a/zrpc/internal/resolver/kube/eventhandler.go b/zrpc/internal/resolver/kube/eventhandler.go
index 977eadca..ae7e6d91 100644
--- a/zrpc/internal/resolver/kube/eventhandler.go
+++ b/zrpc/internal/resolver/kube/eventhandler.go
@@ -8,12 +8,14 @@ import (
 	v1 "k8s.io/api/core/v1"
 )
 
+// EventHandler is ResourceEventHandler implementation.
 type EventHandler struct {
 	update    func([]string)
 	endpoints map[string]lang.PlaceholderType
 	lock      sync.Mutex
 }
 
+// NewEventHandler returns an EventHandler.
 func NewEventHandler(update func([]string)) *EventHandler {
 	return &EventHandler{
 		update:    update,
@@ -21,6 +23,7 @@ func NewEventHandler(update func([]string)) *EventHandler {
 	}
 }
 
+// OnAdd handles the endpoints add events.
 func (h *EventHandler) OnAdd(obj interface{}) {
 	endpoints, ok := obj.(*v1.Endpoints)
 	if !ok {
@@ -46,6 +49,7 @@ func (h *EventHandler) OnAdd(obj interface{}) {
 	}
 }
 
+// OnDelete handles the endpoints delete events.
 func (h *EventHandler) OnDelete(obj interface{}) {
 	endpoints, ok := obj.(*v1.Endpoints)
 	if !ok {
@@ -71,6 +75,7 @@ func (h *EventHandler) OnDelete(obj interface{}) {
 	}
 }
 
+// OnUpdate handles the endpoints update events.
 func (h *EventHandler) OnUpdate(oldObj, newObj interface{}) {
 	oldEndpoints, ok := oldObj.(*v1.Endpoints)
 	if !ok {
@@ -91,6 +96,7 @@ func (h *EventHandler) OnUpdate(oldObj, newObj interface{}) {
 	h.Update(newEndpoints)
 }
 
+// Update updates the endpoints.
 func (h *EventHandler) Update(endpoints *v1.Endpoints) {
 	h.lock.Lock()
 	defer h.lock.Unlock()
diff --git a/zrpc/internal/resolver/kube/targetparser.go b/zrpc/internal/resolver/kube/targetparser.go
index 569fdcd5..66fc6e51 100644
--- a/zrpc/internal/resolver/kube/targetparser.go
+++ b/zrpc/internal/resolver/kube/targetparser.go
@@ -15,12 +15,14 @@ const (
 
 var emptyService Service
 
+// Service represents a service with namespace, name and port.
 type Service struct {
 	Namespace string
 	Name      string
 	Port      int
 }
 
+// ParseTarget parses the resolver.Target.
 func ParseTarget(target resolver.Target) (Service, error) {
 	var service Service
 	service.Namespace = target.Authority
diff --git a/zrpc/internal/serverinterceptors/opentracinginterceptor.go b/zrpc/internal/serverinterceptors/opentracinginterceptor.go
index 5d8b9ae1..904dd634 100644
--- a/zrpc/internal/serverinterceptors/opentracinginterceptor.go
+++ b/zrpc/internal/serverinterceptors/opentracinginterceptor.go
@@ -14,6 +14,7 @@ import (
 	"google.golang.org/grpc/status"
 )
 
+// UnaryOpenTracingInterceptor returns a grpc.UnaryServerInterceptor for opentelemetry.
 func UnaryOpenTracingInterceptor() grpc.UnaryServerInterceptor {
 	propagator := otel.GetTextMapPropagator()
 	return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo,
@@ -24,20 +25,12 @@ func UnaryOpenTracingInterceptor() grpc.UnaryServerInterceptor {
 
 		requestMetadata, _ := metadata.FromIncomingContext(ctx)
 		metadataCopy := requestMetadata.Copy()
-
 		bags, spanCtx := opentelemetry.Extract(ctx, propagator, &metadataCopy)
 		ctx = baggage.ContextWithBaggage(ctx, bags)
-
 		tr := otel.Tracer(opentelemetry.TraceName)
 		name, attr := opentelemetry.SpanInfo(info.FullMethod, opentelemetry.PeerFromCtx(ctx))
-
-		var span trace.Span
-		ctx, span = tr.Start(
-			trace.ContextWithRemoteSpanContext(ctx, spanCtx),
-			name,
-			trace.WithSpanKind(trace.SpanKindServer),
-			trace.WithAttributes(attr...),
-		)
+		ctx, span := tr.Start(trace.ContextWithRemoteSpanContext(ctx, spanCtx), name,
+			trace.WithSpanKind(trace.SpanKindServer), trace.WithAttributes(attr...))
 		defer span.End()
 
 		opentelemetry.MessageReceived.Event(ctx, 1, req)
@@ -57,6 +50,7 @@ func UnaryOpenTracingInterceptor() grpc.UnaryServerInterceptor {
 	}
 }
 
+// StreamOpenTracingInterceptor returns a grpc.StreamServerInterceptor for opentelemetry.
 func StreamOpenTracingInterceptor() grpc.StreamServerInterceptor {
 	propagator := otel.GetTextMapPropagator()
 	return func(srv interface{}, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
@@ -67,30 +61,22 @@ func StreamOpenTracingInterceptor() grpc.StreamServerInterceptor {
 
 		requestMetadata, _ := metadata.FromIncomingContext(ctx)
 		metadataCopy := requestMetadata.Copy()
-
 		bags, spanCtx := opentelemetry.Extract(ctx, propagator, &metadataCopy)
 		ctx = baggage.ContextWithBaggage(ctx, bags)
-
 		tr := otel.Tracer(opentelemetry.TraceName)
 		name, attr := opentelemetry.SpanInfo(info.FullMethod, opentelemetry.PeerFromCtx(ctx))
-		ctx, span := tr.Start(
-			trace.ContextWithRemoteSpanContext(ctx, spanCtx),
-			name,
-			trace.WithSpanKind(trace.SpanKindServer),
-			trace.WithAttributes(attr...),
-		)
+		ctx, span := tr.Start(trace.ContextWithRemoteSpanContext(ctx, spanCtx), name,
+			trace.WithSpanKind(trace.SpanKindServer), trace.WithAttributes(attr...))
 		defer span.End()
 
-		err := handler(srv, opentelemetry.WrapServerStream(ctx, ss))
-
-		if err != nil {
+		if err := handler(srv, opentelemetry.WrapServerStream(ctx, ss)); err != nil {
 			s, _ := status.FromError(err)
 			span.SetStatus(codes.Error, s.Message())
 			span.SetAttributes(opentelemetry.StatusCodeAttr(s.Code()))
-		} else {
-			span.SetAttributes(opentelemetry.StatusCodeAttr(gcodes.OK))
+			return err
 		}
 
-		return err
+		span.SetAttributes(opentelemetry.StatusCodeAttr(gcodes.OK))
+		return nil
 	}
 }