dialect/sql: replace nulltime with official implementation on 1.13 and higher

Summary: Pull Request resolved: https://github.com/facebookincubator/ent/pull/169

Reviewed By: alexsn

Differential Revision: D18561431

fbshipit-source-id: d21335c073e0abed99d97c85c03cfa17c8326fef

dialect/sql/sql_112.go

@@ -0,0 +1,38 @@
+// Copyright 2019-present Facebook Inc. All rights reserved.
+// This source code is licensed under the Apache 2.0 license found
+// in the LICENSE file in the root directory of this source tree.
+
+// +build !go1.13
+
+package sql
+
+import (
+	"database/sql/driver"
+	"time"
+)
+
+// NullTime represents a time.Time that may be null.
+//
+// NullTime implements the Scanner interface so it can
+// be used as a scan destination, similar to NullString.
+type NullTime struct {
+	Time  time.Time
+	Valid bool // Valid is true if Time is not NULL
+}
+
+// Scan implements the Scanner interface.
+func (n *NullTime) Scan(v interface{}) error {
+	if v, ok := v.(time.Time); ok {
+		n.Time = v
+		n.Valid = true
+	}
+	return nil
+}
+
+// Value implements the driver Valuer interface.
+func (n NullTime) Value() (driver.Value, error) {
+	if !n.Valid {
+		return nil, nil
+	}
+	return n.Time, nil
+}