🐛 Fixing a bug. about pointer package function (#230)

update:
1. UnwarpOr
2. UnwarpOrDefault
3. ExtractPointer

add:
1. UnwrapOr
2. IsNil

pointer/pointer_examples_test.go

@@ -90,3 +90,61 @@ func ExampleExtractPointer() {
 	// Output:
 	// 1
 }
+
+func ExampleIsNil() {
+	a := 1
+	b := &a
+	c := &b
+	d := &c
+	e := &d
+	var f *int
+
+	result1 := IsNil(a)
+	result2 := IsNil(b)
+	result3 := IsNil(c)
+	result4 := IsNil(d)
+	result5 := IsNil(e)
+	result6 := IsNil(f)
+	result7 := IsNil(nil)
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+	fmt.Println(result3)
+	fmt.Println(result4)
+	fmt.Println(result5)
+	fmt.Println(result6)
+	fmt.Println(result7)
+
+	// Output:
+	// false
+	// false
+	// false
+	// false
+	// false
+	// true
+	// true
+}
+
+func ExampleUnwrapOr() {
+	a := 123
+	b := "abc"
+
+	var c *int
+	var d *string
+
+	result1 := UnwrapOr(&a, 456)
+	result2 := UnwrapOr(&b, "efg")
+	result3 := UnwrapOr(c, 456)
+	result4 := UnwrapOr(d, "def")
+
+	fmt.Println(result1)
+	fmt.Println(result2)
+	fmt.Println(result3)
+	fmt.Println(result4)
+
+	// Output:
+	// 123
+	// abc
+	// 456
+	// def
+}