diff --git a/signer/jws_test.go b/signer/jws_test.go
index f44ed8f1..729e67ed 100644
--- a/signer/jws_test.go
+++ b/signer/jws_test.go
@@ -4,9 +4,10 @@ import (
 	"crypto/x509"
 	"encoding/json"
 	"errors"
-	"github.com/notaryproject/notation-core-go/internal/testhelper"
 	"reflect"
 	"testing"
+
+	"github.com/notaryproject/notation-core-go/internal/testhelper"
 )
 
 // Tests various scenarios around newJWSEnvelopeFromBytes method
diff --git a/signer/jwt.go b/signer/jwt.go
index eb82c36f..ac39d90b 100644
--- a/signer/jwt.go
+++ b/signer/jwt.go
@@ -6,6 +6,7 @@ import (
 	"crypto/rsa"
 	"encoding/base64"
 	"fmt"
+
 	"github.com/golang-jwt/jwt/v4"
 )
 
diff --git a/signer/signer.go b/signer/signer.go
index c74f8e70..a0213b8b 100644
--- a/signer/signer.go
+++ b/signer/signer.go
@@ -3,8 +3,9 @@ package signer
 import (
 	"crypto/x509"
 	"fmt"
-	nx509 "github.com/notaryproject/notation-core-go/x509"
 	"time"
+
+	nx509 "github.com/notaryproject/notation-core-go/x509"
 )
 
 type SignatureMediaType string
diff --git a/signer/signer_test.go b/signer/signer_test.go
index 0c5e7e74..0310af0a 100644
--- a/signer/signer_test.go
+++ b/signer/signer_test.go
@@ -9,12 +9,13 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"errors"
-	"github.com/notaryproject/notation-core-go/internal/testhelper"
 	"reflect"
 	"sort"
 	"strings"
 	"testing"
 	"time"
+
+	"github.com/notaryproject/notation-core-go/internal/testhelper"
 )
 
 const (
@@ -32,6 +33,7 @@ const (
 var (
 	TestTamperedSig = strings.Replace(TestValidSig, "0fX0", "1fX0=", 1)
 )
+
 func TestNewSignatureEnvelopeFromBytesError(t *testing.T) {
 	_, err := NewSignatureEnvelopeFromBytes([]byte("Malformed"), MediaTypeJWSJson)
 	if !(err != nil && errors.As(err, new(MalformedArgumentError))) {