add nullable type

Signed-off-by: Ashutosh Kumar <sonasingh46@gmail.com>

Author: sonasingh46

types/nullable.go

@@ -0,0 +1,26 @@
+package types
+
+import "encoding/json"
+
+type Nullable[T any] struct {
+	Value T
+	Set   bool
+	Null  bool
+}
+
+func (t *Nullable[T]) UnmarshalJSON(data []byte) error {
+	t.Set = true
+	return json.Unmarshal(data, &t.Value)
+}
+
+func (t Nullable[T]) MarshalJSON() ([]byte, error) {
+	return json.Marshal(t.Value)
+}
+
+func (t *Nullable[T]) IsNullDefined() bool {
+	return t.Set && t.Value == nil
+}
+
+func (t *Nullable[T]) HasValue() bool {
+	return t.Set && t.Value != nil
+}

types/nullable_test.go

@@ -0,0 +1 @@
+package types