style fix for error checking (#1170)

+additional linting

core/data/data_test.go

@@ -16,8 +16,7 @@ func TestString(t *testing.T) {
 	const testKey = "test string key"
 	const testValue = "test string value"
 
-	err := _datastore.SetString(testKey, testValue)
-	if err != nil {
+	if err := _datastore.SetString(testKey, testValue); err != nil {
 		panic(err)
 	}