diff --git a/examples/module1/callbacks/main.go b/examples/module1/callbacks/main.go
index d02fdde..b5cef08 100644
--- a/examples/module1/callbacks/main.go
+++ b/examples/module1/callbacks/main.go
@@ -1,20 +1,20 @@
 package main
 
 func main() {
-	var a *int
-	*a += 1
-	// DoOperation(1, increase)
+	DoOperation(1, increase)
 	DoOperation(1, decrease)
 }
 
 func increase(a, b int) int {
+	println("increase result is:", a+b)
 	return a + b
 }
 
-func DoOperation(y int, f func(int, int)) {
+func DoOperation(y int, f func(int, int) int) {
 	f(y, 1)
 }
 
-func decrease(a, b int) {
+func decrease(a, b int) int {
 	println("decrease result is:", a-b)
+	return a - b
 }
diff --git a/examples/module1/callbacks/main_test.go b/examples/module1/callbacks/main_test.go
index c1950b7..53d5613 100644
--- a/examples/module1/callbacks/main_test.go
+++ b/examples/module1/callbacks/main_test.go
@@ -6,11 +6,8 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func add(a, b int) int {
-	return a + b
-}
 func TestIncrease(t *testing.T) {
 	t.Log("Start testing")
-	result := add(1, 2)
+	result := increase(1, 2)
 	assert.Equal(t, result, 3)
 }
diff --git a/examples/module1/interface/main.go b/examples/module1/interface/main.go
index d81e76d..3a23440 100644
--- a/examples/module1/interface/main.go
+++ b/examples/module1/interface/main.go
@@ -6,6 +6,20 @@ type IF interface {
 	getName() string
 }
 
+type Fruit interface {
+	Describe() string
+}
+
+type Apple struct {
+	Color string
+	Shape string
+	Taste string
+}
+
+func (a Apple) Describe() string {
+	return fmt.Sprintf("Apple: the color is %s, the shape is %s, the taste is %s", a.Color, a.Shape, a.Taste)
+}
+
 type Human struct {
 	firstName, lastName string
 }
@@ -32,7 +46,7 @@ func (c *Car) getName() string {
 }
 
 func main() {
-	interfaces := []IF{}
+	var interfaces []IF
 	h := new(Human)
 	h.firstName = "first"
 	h.lastName = "last"
@@ -48,4 +62,11 @@ func main() {
 	p.vendor = "testVendor"
 	p.model = "testModel"
 	fmt.Println(p.getName())
+
+	apple := new(Apple)
+	apple.Color = "Red"
+	apple.Shape = "Round"
+	apple.Taste = "Sweet"
+	description := apple.Describe()
+	fmt.Print(description)
 }
diff --git a/examples/module1/slice/makenew/main.go b/examples/module1/slice/makenew/main.go
index b4cca47..d773aa3 100644
--- a/examples/module1/slice/makenew/main.go
+++ b/examples/module1/slice/makenew/main.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"reflect"
 )
 
 func main() {
@@ -9,8 +10,8 @@ func main() {
 	mySlice2 := make([]int, 0)
 	mySlice3 := make([]int, 10)
 	mySlice4 := make([]int, 10, 20)
-	fmt.Printf("mySlice1 %+v\n", mySlice1)
-	fmt.Printf("mySlice2 %+v\n", mySlice2)
+	fmt.Printf("mySlice1 %+v\n", reflect.TypeOf(mySlice1))
+	fmt.Printf("mySlice2 %+v\n", reflect.TypeOf(mySlice2))
 	fmt.Printf("mySlice3 %+v\n", mySlice3)
 	fmt.Printf("mySlice4 %+v\n", mySlice4)
 }
diff --git a/go.sum b/go.sum
index 4badd68..ba06ac8 100644
--- a/go.sum
+++ b/go.sum
@@ -7,6 +7,7 @@ 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 v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=