Nil time (#82)

* Handle nil *time.Time Literal (PR #52) + test

* Added sql to test

HISTORY.md

@@ -1,3 +1,7 @@
+## v6.1.0
+
+* Handle nil *time.Time Literal [#73](https://github.com/doug-martin/goqu/pull/73) and [#52](https://github.com/doug-martin/goqu/pull/52) - [@RoarkeRandall](https://github.com/RoarkeRandall) and [@quetz](https://github.com/quetz)
+
 ## v6.0.0
 
 * Updated go support to `1.10`, `1.11` and `1.12`

dataset.go

@@ -229,6 +229,9 @@ func (me *Dataset) Literal(buf *SqlBuilder, val interface{}) error {
 	} else if v, ok := val.(time.Time); ok {
 		return me.adapter.LiteralTime(buf, v)
 	} else if v, ok := val.(*time.Time); ok {
+		if v == nil {
+			return me.adapter.LiteralNil(buf)
+		}
 		return me.adapter.LiteralTime(buf, *v)
 	} else if v, ok := val.(driver.Valuer); ok {
 		dVal, err := v.Value()

dataset_insert_test.go

@@ -8,6 +8,17 @@ import (
 	"time"
 )
 
+func (me *datasetTest) TestInsertNullTime() {
+	t := me.T()
+	ds1 := From("items")
+	type item struct {
+		CreatedAt *time.Time `db:"created_at"`
+	}
+	sql, _, err := ds1.ToInsertSql(item{CreatedAt: nil})
+	assert.NoError(t, err)
+	assert.Equal(t, sql, `INSERT INTO "items" ("created_at") VALUES (NULL)`)
+}
+
 func (me *datasetTest) TestInsertSqlNoReturning() {
 	t := me.T()
 	mDb, _, _ := sqlmock.New()