go/arrow/array: fix ref-count for Struct array

Author: sbinet

go/arrow/array/struct.go

@@ -65,6 +65,13 @@ func (a *Struct) setData(data *Data) {
 	}
 }
 
+func (a *Struct) Retain() {
+	a.array.Retain()
+	for _, f := range a.fields {
+		f.Retain()
+	}
+}
+
 func (a *Struct) Release() {
 	a.array.Release()
 	for _, f := range a.fields {

go/arrow/array/struct_test.go

@@ -79,6 +79,9 @@ func TestStructArray(t *testing.T) {
 		arr := sb.NewArray().(*array.Struct)
 		defer arr.Release()
 
+		arr.Retain()
+		arr.Release()
+
 		if got, want := arr.DataType().ID(), arrow.STRUCT; got != want {
 			t.Fatalf("got=%v, want=%v", got, want)
 		}