diff --git a/app.go b/app.go
index 885328910..2fa52ec9b 100644
--- a/app.go
+++ b/app.go
@@ -30,7 +30,7 @@ type AppInfo interface {
 type App struct {
 	opts     options
 	ctx      context.Context
-	cancel   func()
+	cancel   context.CancelFunc
 	mu       sync.Mutex
 	instance *registry.ServiceInstance
 }
diff --git a/contrib/config/consul/config.go b/contrib/config/consul/config.go
index 0404801bc..108f00828 100644
--- a/contrib/config/consul/config.go
+++ b/contrib/config/consul/config.go
@@ -11,7 +11,7 @@ import (
 	"github.com/go-kratos/kratos/v2/config"
 )
 
-// Option is etcd config option.
+// Option is consul config option.
 type Option func(o *options)
 
 type options struct {
diff --git a/contrib/registry/eureka/eureka.go b/contrib/registry/eureka/eureka.go
index a7759dee4..530b638c9 100644
--- a/contrib/registry/eureka/eureka.go
+++ b/contrib/registry/eureka/eureka.go
@@ -58,9 +58,9 @@ func (e *API) broadcast() {
 	for _, subscriber := range e.subscribers {
 		go subscriber.callBack()
 	}
-	defer e.lock.Unlock()
 	e.lock.Lock()
 	e.allInstances = instances
+	e.lock.Unlock()
 }
 
 func (e *API) cacheAllInstances() map[string][]Instance {
@@ -106,12 +106,12 @@ func (e *API) Deregister(ctx context.Context, endpoints []Endpoint) error {
 
 func (e *API) Subscribe(serverName string, fn func()) error {
 	e.lock.Lock()
-	defer e.lock.Unlock()
 	appID := e.ToAppID(serverName)
 	e.subscribers[appID] = &subscriber{
 		appID:    appID,
 		callBack: fn,
 	}
+	e.lock.Unlock()
 	go e.broadcast()
 	return nil
 }
@@ -128,8 +128,8 @@ func (e *API) GetService(ctx context.Context, serverName string) []Instance {
 
 func (e *API) Unsubscribe(serverName string) {
 	e.lock.Lock()
-	defer e.lock.Unlock()
 	delete(e.subscribers, e.ToAppID(serverName))
+	e.lock.Unlock()
 }
 
 func (e *API) ToAppID(serverName string) string {
diff --git a/contrib/registry/eureka/register.go b/contrib/registry/eureka/register.go
index 242ec9105..f7226ce25 100644
--- a/contrib/registry/eureka/register.go
+++ b/contrib/registry/eureka/register.go
@@ -54,7 +54,11 @@ func New(eurekaUrls []string, opts ...Option) (*Registry, error) {
 		o(r)
 	}
 
-	client := NewClient(eurekaUrls, WithHeartbeatInterval(r.heartbeatInterval), WithClientContext(r.ctx), WithNamespace(r.eurekaPath))
+	client := NewClient(eurekaUrls,
+		WithHeartbeatInterval(r.heartbeatInterval),
+		WithClientContext(r.ctx),
+		WithNamespace(r.eurekaPath),
+	)
 	r.api = NewAPI(r.ctx, client, r.refreshInterval)
 	return r, nil
 }
diff --git a/contrib/registry/polaris/registry.go b/contrib/registry/polaris/registry.go
index d9b87150c..e968fe386 100644
--- a/contrib/registry/polaris/registry.go
+++ b/contrib/registry/polaris/registry.go
@@ -376,7 +376,7 @@ func (w *Watcher) Next() ([]*registry.ServiceInstance, error) {
 							if serviceInstance.ID == instance.GetId() {
 								// remove equal
 								if len(w.ServiceInstances) <= 1 {
-									w.ServiceInstances = w.ServiceInstances[0:0]
+									w.ServiceInstances = w.ServiceInstances[:0]
 									continue
 								}
 								w.ServiceInstances = append(w.ServiceInstances[:i], w.ServiceInstances[i+1:]...)
diff --git a/selector/filter/version.go b/selector/filter/version.go
index 21f8518ae..a5374470c 100644
--- a/selector/filter/version.go
+++ b/selector/filter/version.go
@@ -9,7 +9,7 @@ import (
 // Version is version filter.
 func Version(version string) selector.NodeFilter {
 	return func(_ context.Context, nodes []selector.Node) []selector.Node {
-		newNodes := make([]selector.Node, 0)
+		newNodes := make([]selector.Node, 0, len(nodes))
 		for _, n := range nodes {
 			if n.Version() == version {
 				newNodes = append(newNodes, n)
diff --git a/transport/grpc/client.go b/transport/grpc/client.go
index d3c246177..edc57d3ef 100644
--- a/transport/grpc/client.go
+++ b/transport/grpc/client.go
@@ -39,7 +39,7 @@ func WithEndpoint(endpoint string) ClientOption {
 	}
 }
 
-// WithSubset with client disocvery subset size.
+// WithSubset with client discovery subset size.
 // zero value means subset filter disabled
 func WithSubset(size int) ClientOption {
 	return func(o *clientOptions) {
diff --git a/transport/grpc/resolver/direct/builder.go b/transport/grpc/resolver/direct/builder.go
index ebbd22d7a..a81b77af4 100644
--- a/transport/grpc/resolver/direct/builder.go
+++ b/transport/grpc/resolver/direct/builder.go
@@ -6,6 +6,8 @@ import (
 	"google.golang.org/grpc/resolver"
 )
 
+const name = "direct"
+
 func init() {
 	resolver.Register(NewBuilder())
 }
@@ -35,5 +37,5 @@ func (d *directBuilder) Build(target resolver.Target, cc resolver.ClientConn, _
 }
 
 func (d *directBuilder) Scheme() string {
-	return "direct"
+	return name
 }
diff --git a/transport/grpc/resolver/discovery/builder_test.go b/transport/grpc/resolver/discovery/builder_test.go
index e216a5445..640510518 100644
--- a/transport/grpc/resolver/discovery/builder_test.go
+++ b/transport/grpc/resolver/discovery/builder_test.go
@@ -38,6 +38,14 @@ func TestDisableDebugLog(t *testing.T) {
 	}
 }
 
+func TestPrintDebugLog(t *testing.T) {
+	o := &builder{}
+	PrintDebugLog(true)(o)
+	if !o.debugLog {
+		t.Errorf("expected PrintdebugLog true, got %v", o.debugLog)
+	}
+}
+
 type mockDiscovery struct{}
 
 func (m *mockDiscovery) GetService(_ context.Context, _ string) ([]*registry.ServiceInstance, error) {
diff --git a/transport/http/client.go b/transport/http/client.go
index 7784a1c27..2d013ffad 100644
--- a/transport/http/client.go
+++ b/transport/http/client.go
@@ -56,7 +56,7 @@ type clientOptions struct {
 	subsetSize   int
 }
 
-// WithSubset with client disocvery subset size.
+// WithSubset with client discovery subset size.
 // zero value means subset filter disabled
 func WithSubset(size int) ClientOption {
 	return func(o *clientOptions) {
diff --git a/transport/http/resolver.go b/transport/http/resolver.go
index bcbf8f3b3..e0db0cb67 100644
--- a/transport/http/resolver.go
+++ b/transport/http/resolver.go
@@ -56,7 +56,7 @@ type resolver struct {
 func newResolver(ctx context.Context, discovery registry.Discovery, target *Target,
 	rebalancer selector.Rebalancer, block, insecure bool, subsetSize int,
 ) (*resolver, error) {
-	// this is new resovler
+	// this is new resolver
 	watcher, err := discovery.Watch(ctx, target.Endpoint)
 	if err != nil {
 		return nil, err
diff --git a/transport/http/server.go b/transport/http/server.go
index 9958a08a8..c967e4a1b 100644
--- a/transport/http/server.go
+++ b/transport/http/server.go
@@ -134,7 +134,7 @@ func Listener(lis net.Listener) ServerOption {
 	}
 }
 
-// PathPrefix with mux's PathPrefix, router will replaced by a subrouter that start with prefix.
+// PathPrefix with mux's PathPrefix, router will be replaced by a subrouter that start with prefix.
 func PathPrefix(prefix string) ServerOption {
 	return func(s *Server) {
 		s.router = s.router.PathPrefix(prefix).Subrouter()