diff --git a/.travis.yml b/.travis.yml
index c398289..420bcc9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,7 +3,9 @@ sudo: required
 
 go:
   - "1.12"
+  - "1.13"
   - master
 
 script:
-  - make test
\ No newline at end of file
+  - curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(go env GOPATH)/bin v1.21.0
+  - make lint && make test
\ No newline at end of file
diff --git a/Makefile b/Makefile
index d229787..3d319bb 100644
--- a/Makefile
+++ b/Makefile
@@ -14,4 +14,7 @@ bench:
 	go test -bench=. ./...
 
 release:
-	go mod tidy
\ No newline at end of file
+	go mod tidy
+
+lint:
+	golangci-lint run
\ No newline at end of file
diff --git a/README.md b/README.md
index a12db0c..e7a1e28 100644
--- a/README.md
+++ b/README.md
@@ -17,15 +17,15 @@ import (
 
 func main() {
 
-	d := elton.New()
-	d.Use(etag.NewDefault())
+	e := elton.New()
+	e.Use(etag.NewDefault())
 
-	d.GET("/", func(c *elton.Context) (err error) {
+	e.GET("/", func(c *elton.Context) (err error) {
 		c.BodyBuffer = bytes.NewBufferString("abcd")
 		return
 	})
 
-	d.ListenAndServe(":7001")
+	e.ListenAndServe(":3000")
 }
 
 ```
diff --git a/etag.go b/etag.go
index f9eb68f..accf7f2 100644
--- a/etag.go
+++ b/etag.go
@@ -37,7 +37,10 @@ func gen(buf []byte) string {
 		return `"0-2jmj7l5rSw0yVb_vlWAYkK_YBwk="`
 	}
 	h := sha1.New()
-	h.Write(buf)
+	_, err := h.Write(buf)
+	if err != nil {
+		return ""
+	}
 	hash := base64.URLEncoding.EncodeToString(h.Sum(nil))
 	return fmt.Sprintf(`"%x-%s"`, size, hash)
 }
@@ -77,7 +80,9 @@ func New(config Config) elton.Handler {
 			return
 		}
 		eTag := gen(bodyBuf.Bytes())
-		c.SetHeader(elton.HeaderETag, eTag)
+		if eTag != "" {
+			c.SetHeader(elton.HeaderETag, eTag)
+		}
 		return
 	}
 }
diff --git a/etag_test.go b/etag_test.go
index dfaf788..c5503cf 100644
--- a/etag_test.go
+++ b/etag_test.go
@@ -113,7 +113,7 @@ func BenchmarkMd5(b *testing.B) {
 			return `"0-2jmj7l5rSw0yVb_vlWAYkK_YBwk="`
 		}
 		h := md5.New()
-		h.Write(buf)
+		_, _ = h.Write(buf)
 		hash := base64.URLEncoding.EncodeToString(h.Sum(nil))
 		return fmt.Sprintf(`"%x-%s"`, size, hash)
 	}
diff --git a/example/main.go b/example/main.go
new file mode 100644
index 0000000..1c9ec7c
--- /dev/null
+++ b/example/main.go
@@ -0,0 +1,24 @@
+package main
+
+import (
+	"bytes"
+
+	"github.com/vicanso/elton"
+	etag "github.com/vicanso/elton-etag"
+)
+
+func main() {
+	e := elton.New()
+
+	e.Use(etag.NewDefault())
+
+	e.GET("/", func(c *elton.Context) (err error) {
+		c.BodyBuffer = bytes.NewBufferString("abcd")
+		return
+	})
+
+	err := e.ListenAndServe(":3000")
+	if err != nil {
+		panic(err)
+	}
+}
diff --git a/go.mod b/go.mod
index ec34e5e..685b752 100644
--- a/go.mod
+++ b/go.mod
@@ -3,6 +3,6 @@ module github.com/vicanso/elton-etag
 go 1.12
 
 require (
-	github.com/stretchr/testify v1.3.0
-	github.com/vicanso/elton v0.2.0
+	github.com/stretchr/testify v1.4.0
+	github.com/vicanso/elton v0.2.1
 )
diff --git a/go.sum b/go.sum
index c2e96a9..5d84ce0 100644
--- a/go.sum
+++ b/go.sum
@@ -7,9 +7,16 @@ github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZN
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
+github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 github.com/vicanso/elton v0.2.0 h1:QlXgmq6m+9wZN7FeLD25/EhBkl8blzppviVY5U5PTm0=
 github.com/vicanso/elton v0.2.0/go.mod h1:ynAUOSkZQ+pFaUsxlG5hYnJFjPpMwz8YyEBPzNh0pSg=
+github.com/vicanso/elton v0.2.1 h1:OrfDjNjXL6KzUhAuAFwCQIa6guXXd7OY+L4ZgH16Rpc=
+github.com/vicanso/elton v0.2.1/go.mod h1:ynAUOSkZQ+pFaUsxlG5hYnJFjPpMwz8YyEBPzNh0pSg=
 github.com/vicanso/hes v0.2.1 h1:jRFEADmiQ30koVY/sKwlkhyXM5B3QbVVizLqrjNJgPw=
 github.com/vicanso/hes v0.2.1/go.mod h1:QcxOFmFfBQMhASTaLgnFayXYCgevdSeBVprt+o+3eKo=
 github.com/vicanso/keygrip v0.1.0 h1:/zYzoVIbREAvaxSM7bo3/oSXuuYztaP71dPBfhRoNkM=
 github.com/vicanso/keygrip v0.1.0/go.mod h1:cI05iOjY00NJ7oH2Z9Zdm9eJPUkpoex3XnEubK78nho=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=