[StructUtil] add support that the Struct can nest any type to transform (#80)

* add support json tag attribute for StructToMap function

* add the structutil to provide more rich functions and fixed #77

* add support that the nested struct to map for structutil

* recover code

* add structutil unit test

* [StructUtil] add unit test

pointer/pointer.go

@@ -0,0 +1,14 @@
+package pointer
+
+import "reflect"
+
+// ExtractPointer returns the underlying value by the given interface type
+func ExtractPointer(value any) any {
+	t := reflect.TypeOf(value)
+	v := reflect.ValueOf(value)
+
+	if t.Kind() != reflect.Pointer {
+		return value
+	}
+	return ExtractPointer(v.Elem().Interface())
+}

pointer/pointer_test.go

@@ -0,0 +1,18 @@
+package pointer
+
+import (
+	"github.com/duke-git/lancet/v2/internal"
+	"testing"
+)
+
+func TestExtractPointer(t *testing.T) {
+
+	assert := internal.NewAssert(t, "TestExtractPointer")
+
+	a := 1
+	b := &a
+	c := &b
+	d := &c
+
+	assert.Equal(1, ExtractPointer(d))
+}