Add Gob encoding functions for Key.

service/datastore/key.go

Index: service/datastore/key.go
diff --git a/service/datastore/key.go b/service/datastore/key.go
index b2b9e45f37da085b33f76f68f0f7d9ea5b791dc5..227858858bc76da9850d0ecb019ca1ed6eac8320 100644
--- a/service/datastore/key.go
+++ b/service/datastore/key.go
@@ -320,6 +320,21 @@ func (k *Key) UnmarshalJSON(buf []byte) error {
 	return nil
 }
 
+// GobEncode allows the Key to be encoded in a Gob struct.
+func (k *Key) GobEncode() ([]byte, error) {
+	return []byte(k.Encode()), nil
+}
+
+// GobDecode allows the Key to be decoded in a Gob struct.
+func (k *Key) GobDecode(buf []byte) error {
+	nk, err := NewKeyEncoded(string(buf))
+	if err != nil {
+		return err
+	}
+	*k = *nk
+	return nil
+}
+
 // Root returns the entity root for the given key.
 func (k *Key) Root() *Key {
 	if len(k.toks) > 1 {