diff --git a/core/discov/config.go b/core/discov/config.go
index c1f6b7b1..1557b4f8 100644
--- a/core/discov/config.go
+++ b/core/discov/config.go
@@ -2,6 +2,13 @@ package discov
 
 import "errors"
 
+var (
+	// errEmptyEtcdHosts indicates that etcd hosts are empty.
+	errEmptyEtcdHosts = errors.New("empty etcd hosts")
+	// errEmptyEtcdKey indicates that etcd key is empty.
+	errEmptyEtcdKey = errors.New("empty etcd key")
+)
+
 // EtcdConf is the config item with the given key on etcd.
 type EtcdConf struct {
 	Hosts              []string
@@ -27,9 +34,9 @@ func (c EtcdConf) HasTLS() bool {
 // Validate validates c.
 func (c EtcdConf) Validate() error {
 	if len(c.Hosts) == 0 {
-		return errors.New("empty etcd hosts")
+		return errEmptyEtcdHosts
 	} else if len(c.Key) == 0 {
-		return errors.New("empty etcd key")
+		return errEmptyEtcdKey
 	} else {
 		return nil
 	}
diff --git a/core/filex/rangereader.go b/core/filex/rangereader.go
index cd69f678..0a962e51 100644
--- a/core/filex/rangereader.go
+++ b/core/filex/rangereader.go
@@ -5,6 +5,9 @@ import (
 	"os"
 )
 
+// errExceedFileSize indicates that the file size is exceeded.
+var errExceedFileSize = errors.New("exceed file size")
+
 // A RangeReader is used to read a range of content from a file.
 type RangeReader struct {
 	file  *os.File
@@ -29,7 +32,7 @@ func (rr *RangeReader) Read(p []byte) (n int, err error) {
 	}
 
 	if rr.stop < rr.start || rr.start >= stat.Size() {
-		return 0, errors.New("exceed file size")
+		return 0, errExceedFileSize
 	}
 
 	if rr.stop-rr.start < int64(len(p)) {
diff --git a/core/jsonx/json.go b/core/jsonx/json.go
index c4f60b68..176e30a0 100644
--- a/core/jsonx/json.go
+++ b/core/jsonx/json.go
@@ -51,5 +51,5 @@ func unmarshalUseNumber(decoder *json.Decoder, v interface{}) error {
 }
 
 func formatError(v string, err error) error {
-	return fmt.Errorf("string: `%s`, error: `%s`", v, err.Error())
+	return fmt.Errorf("string: `%s`, error: `%w`", v, err)
 }
diff --git a/core/timex/ticker.go b/core/timex/ticker.go
index 59b5eb9d..2691a030 100644
--- a/core/timex/ticker.go
+++ b/core/timex/ticker.go
@@ -7,6 +7,9 @@ import (
 	"github.com/zeromicro/go-zero/core/lang"
 )
 
+// errTimeout indicates a timeout.
+var errTimeout = errors.New("timeout")
+
 type (
 	// Ticker interface wraps the Chan and Stop methods.
 	Ticker interface {
@@ -70,7 +73,7 @@ func (ft *fakeTicker) Tick() {
 func (ft *fakeTicker) Wait(d time.Duration) error {
 	select {
 	case <-time.After(d):
-		return errors.New("timeout")
+		return errTimeout
 	case <-ft.done:
 		return nil
 	}