Fix lint and format code in core dir

core/config/json/json.go

@@ -31,8 +31,7 @@ import (
 )
 
 // JSONConfig is a json config parser and implements Config interface.
-type JSONConfig struct {
-}
+type JSONConfig struct{}
 
 // Parse returns a ConfigContainer with parsed json config map.
 func (js *JSONConfig) Parse(filename string) (config.Configer, error) {

core/config/json/json_test.go

@@ -25,7 +25,6 @@ import (
 )
 
 func TestJsonStartsWithArray(t *testing.T) {
-
 	const jsoncontextwitharray = `[
 	{
 		"url": "user",
@@ -72,7 +71,6 @@ func TestJsonStartsWithArray(t *testing.T) {
 }
 
 func TestJson(t *testing.T) {
-
 	var (
 		jsoncontext = `{
 "appname": "beeapi",