Add StructUtil for provide more rich functions (#79)

* add support json tag attribute for StructToMap function

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

structutil/field.go

@@ -0,0 +1,55 @@
+package structutil
+
+import "reflect"
+
+type Field struct {
+	value reflect.Value
+	field reflect.StructField
+	tag   *Tag
+}
+
+func newField(v reflect.Value, f reflect.StructField, tagName string) *Field {
+	tag := f.Tag.Get(tagName)
+	return &Field{
+		value: v,
+		field: f,
+		tag:   newTag(tag),
+	}
+}
+
+// Tag returns the value that the key in the tag string.
+func (f *Field) Tag() *Tag {
+	return f.tag
+}
+
+// Value returns the underlying value of the field.
+func (f *Field) Value() any {
+	return f.value.Interface()
+}
+
+// IsEmbedded returns true if the given field is an embedded field.
+func (f *Field) IsEmbedded() bool {
+	return f.field.Anonymous
+}
+
+// IsExported returns true if the given field is exported.
+func (f *Field) IsExported() bool {
+	return f.field.PkgPath == ""
+}
+
+// IsZero returns true if the given field is zero value.
+func (f *Field) IsZero() bool {
+	z := reflect.Zero(f.value.Type()).Interface()
+	v := f.Value()
+	return reflect.DeepEqual(z, v)
+}
+
+// Name returns the name of the given field
+func (f *Field) Name() string {
+	return f.field.Name
+}
+
+// Kind returns the field's kind
+func (f *Field) Kind() reflect.Kind {
+	return f.value.Kind()
+}