Add database/sql support to pgtype

pgtype/json.go

@@ -1,7 +1,9 @@
 package pgtype
 
 import (
+	"database/sql/driver"
 	"encoding/json"
+	"fmt"
 	"io"
 )
 
@@ -11,6 +13,11 @@ type Json struct {
 }
 
 func (dst *Json) Set(src interface{}) error {
+	if src == nil {
+		*dst = Json{Status: Null}
+		return nil
+	}
+
 	switch value := src.(type) {
 	case string:
 		*dst = Json{Bytes: []byte(value), Status: Present}
@@ -116,3 +123,32 @@ func (src Json) EncodeText(ci *ConnInfo, w io.Writer) (bool, error) {
 func (src Json) EncodeBinary(ci *ConnInfo, w io.Writer) (bool, error) {
 	return src.EncodeText(ci, w)
 }
+
+// Scan implements the database/sql Scanner interface.
+func (dst *Json) Scan(src interface{}) error {
+	if src == nil {
+		*dst = Json{Status: Null}
+		return nil
+	}
+
+	switch src := src.(type) {
+	case string:
+		return dst.DecodeText(nil, []byte(src))
+	case []byte:
+		return dst.DecodeText(nil, src)
+	}
+
+	return fmt.Errorf("cannot scan %T", src)
+}
+
+// Value implements the database/sql/driver Valuer interface.
+func (src Json) Value() (driver.Value, error) {
+	switch src.Status {
+	case Present:
+		return src.Bytes, nil
+	case Null:
+		return nil, nil
+	default:
+		return nil, errUndefined
+	}
+}