diff --git a/captcha.go b/captcha.go
index b01b5d8..fc4e5d6 100644
--- a/captcha.go
+++ b/captcha.go
@@ -22,8 +22,11 @@ import (
 
 const charPreset = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
 
-var rng = rand.New(rand.NewSource(time.Now().UnixNano()))
-var ttfFont *truetype.Font
+// nolint: gochecknoglobals
+var (
+	rng     = rand.New(rand.NewSource(time.Now().UnixNano()))
+	ttfFont *truetype.Font
+)
 
 // Options manage captcha generation details.
 type Options struct {
@@ -103,6 +106,7 @@ func (data *Data) WriteGIF(w io.Writer, o *gif.Options) error {
 	return gif.Encode(w, data.img, o)
 }
 
+// nolint: gochecknoinits
 func init() {
 	ttfFont, _ = freetype.ParseFont(ttf)
 }
@@ -223,7 +227,7 @@ func drawSineCurve(img *image.NRGBA, opts *Options) {
 	}
 }
 
-func drawText(text string, img *image.NRGBA, opts *Options) error {
+func drawText(text string, img *image.NRGBA, opts *Options) error { // nolint: interfacer
 	ctx := freetype.NewContext()
 	ctx.SetDPI(opts.FontDPI)
 	ctx.SetClip(img.Bounds())
diff --git a/captcha_test.go b/captcha_test.go
index 26b96f7..74fc4cb 100644
--- a/captcha_test.go
+++ b/captcha_test.go
@@ -19,6 +19,7 @@ func TestNewCaptcha(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+
 	buf := new(bytes.Buffer)
 	err = data.WriteImage(buf)
 	if err != nil {
@@ -38,6 +39,7 @@ func TestEncodeJPG(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+
 	buf := new(bytes.Buffer)
 	err = data.WriteJPG(buf, &jpeg.Options{Quality: 70})
 	if err != nil {
@@ -50,25 +52,32 @@ func TestEncodeGIF(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+
 	buf := new(bytes.Buffer)
-	err = data.WriteGIF(buf, &gif.Options{})
+	err = data.WriteGIF(buf, new(gif.Options))
 	if err != nil {
 		t.Fatal(err)
 	}
 }
 
 func TestNewCaptchaOptions(t *testing.T) {
-	New(100, 34, func(options *Options) {
+	_, err := New(100, 34, func(options *Options) {
 		options.BackgroundColor = color.Opaque
 		options.CharPreset = "1234567890"
 		options.CurveNumber = 0
 		options.TextLength = 6
 		options.Palette = palette.WebSafe
 	})
+	if err != nil {
+		t.Fatal(err)
+	}
 
-	NewMathExpr(100, 34, func(options *Options) {
+	_, err = NewMathExpr(100, 34, func(options *Options) {
 		options.BackgroundColor = color.Black
 	})
+	if err != nil {
+		t.Fatal(err)
+	}
 }
 
 func TestNewMathExpr(t *testing.T) {
@@ -132,19 +141,21 @@ func TestLoadFontFromReader(t *testing.T) {
 }
 
 func TestMaxColor(t *testing.T) {
-	var result uint32
-	result = maxColor()
+	result := maxColor()
 	if result != 0 {
 		t.Fatalf("Expect max color to be 0, got %v", result)
 	}
+
 	result = maxColor(1)
 	if result != 1 {
 		t.Fatalf("Expect max color to be 1, got %v", result)
 	}
+
 	result = maxColor(52428, 65535)
 	if result != 255 {
 		t.Fatalf("Expect max color to be 255, got %v", result)
 	}
+
 	var rng = rand.New(rand.NewSource(0))
 	for i := 0; i < 10; i++ {
 		result = maxColor(rng.Uint32(), rng.Uint32(), rng.Uint32())
@@ -155,19 +166,21 @@ func TestMaxColor(t *testing.T) {
 }
 
 func TestMinColor(t *testing.T) {
-	var result uint32
-	result = minColor()
+	result := minColor()
 	if result != 255 {
 		t.Fatalf("Expect min color to be 255, got %v", result)
 	}
+
 	result = minColor(1)
 	if result != 1 {
 		t.Fatalf("Expect min color to be 1, got %v", result)
 	}
+
 	result = minColor(52428, 65535)
 	if result != 204 {
 		t.Fatalf("Expect min color to be 1, got %v", result)
 	}
+
 	var rng = rand.New(rand.NewSource(0))
 	for i := 0; i < 10; i++ {
 		result = minColor(rng.Uint32(), rng.Uint32(), rng.Uint32())
diff --git a/example/basic/main.go b/example/basic/main.go
index d7f8790..ddd400e 100644
--- a/example/basic/main.go
+++ b/example/basic/main.go
@@ -12,6 +12,7 @@ func main() {
 	http.HandleFunc("/", indexHandle)
 	http.HandleFunc("/captcha-default", captchaHandle)
 	http.HandleFunc("/captcha-math", mathHandle)
+
 	fmt.Println("Server start at port 8080")
 	err := http.ListenAndServe(":8080", nil)
 	if err != nil {
@@ -23,9 +24,16 @@ func indexHandle(w http.ResponseWriter, _ *http.Request) {
 	doc, err := template.ParseFiles("index.html")
 	if err != nil {
 		fmt.Fprint(w, err.Error())
+
+		return
+	}
+
+	err = doc.Execute(w, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+
 		return
 	}
-	doc.Execute(w, nil)
 }
 
 func captchaHandle(w http.ResponseWriter, _ *http.Request) {
@@ -33,9 +41,16 @@ func captchaHandle(w http.ResponseWriter, _ *http.Request) {
 	if err != nil {
 		fmt.Fprint(w, nil)
 		fmt.Println(err.Error())
+
+		return
+	}
+
+	err = img.WriteImage(w)
+	if err != nil {
+		fmt.Println(err.Error())
+
 		return
 	}
-	img.WriteImage(w)
 }
 
 func mathHandle(w http.ResponseWriter, _ *http.Request) {
@@ -45,5 +60,11 @@ func mathHandle(w http.ResponseWriter, _ *http.Request) {
 		fmt.Println(err.Error())
 		return
 	}
-	img.WriteImage(w)
+
+	err = img.WriteImage(w)
+	if err != nil {
+		fmt.Println(err.Error())
+
+		return
+	}
 }
diff --git a/example/load-font/main.go b/example/load-font/main.go
index ba5820e..cf4113c 100644
--- a/example/load-font/main.go
+++ b/example/load-font/main.go
@@ -17,6 +17,7 @@ func main() {
 
 	http.HandleFunc("/", indexHandle)
 	http.HandleFunc("/captcha", captchaHandle)
+
 	fmt.Println("Server start at port 8080")
 	err = http.ListenAndServe(":8080", nil)
 	if err != nil {
@@ -28,9 +29,16 @@ func indexHandle(w http.ResponseWriter, _ *http.Request) {
 	doc, err := template.ParseFiles("index.html")
 	if err != nil {
 		fmt.Fprint(w, err.Error())
+
+		return
+	}
+
+	err = doc.Execute(w, nil)
+	if err != nil {
+		fmt.Println(err.Error())
+
 		return
 	}
-	doc.Execute(w, nil)
 }
 
 func captchaHandle(w http.ResponseWriter, _ *http.Request) {
@@ -40,7 +48,14 @@ func captchaHandle(w http.ResponseWriter, _ *http.Request) {
 	if err != nil {
 		fmt.Fprint(w, nil)
 		fmt.Println(err.Error())
+
+		return
+	}
+
+	err = img.WriteImage(w)
+	if err != nil {
+		fmt.Println(err.Error())
+
 		return
 	}
-	img.WriteImage(w)
 }
diff --git a/hsva.go b/hsva.go
index 3035419..42ecdd6 100644
--- a/hsva.go
+++ b/hsva.go
@@ -39,5 +39,6 @@ func (c hsva) RGBA() (r, g, b, a uint32) {
 	b |= b << 8
 	a = uint32(c.a)
 	a |= a << 8
-	return
+
+	return r, g, b, a
 }
diff --git a/hsva_test.go b/hsva_test.go
index 2f4e353..d7cbd92 100644
--- a/hsva_test.go
+++ b/hsva_test.go
@@ -6,7 +6,7 @@ import (
 	"testing"
 )
 
-func TestHSVAInterface(t *testing.T) {
+func TestHSVAInterface(_ *testing.T) {
 	var _ color.Color = hsva{}
 }