Angular 6 - Unexpected token in JSON at position 0

My Angular 5 project was working without issues, just
after having updated it to version 6, it stopped building using ng
build due to the next:

readability="6">

ERROR in ./src/app/assets/i18/en.json
Module parse failed: Unexpected
token in JSON at position 0 You may need an
appropriate loader to
handle this file
type.

here is my
json
file:

{
 "app":
            {
 "Welcome": "Welcome",

 "New": "New"

            },
 "mainMenu": {
 "Home": "Home",
 "Logout":
            "Logout"
 },
 "pageHeader": {
 "About":
            "About",
 "Settings": "Settings"

            }

}

Most
solutions on the web are talking about href="https://github.com/webpack-contrib/copy-webpack-plugin" rel="nofollow
noreferrer">CopyWebpackPlugin but the project doesn't use any Webpack
configuration file.

then, following href="https://stackoverflow.com/questions/5034444/can-json-start-with?answertab=active#tab-top">this
link I tried to make the json as an
array:

{

            "menu":[
 "app": {

 "Welcome": "Welcome",

            "New": "New"
 },
 "mainMenu": {
 "Home":
            "Home",
 "Logout": "Logout"
 },
 "pageHeader":
            {
 "About": "About",
 "Settings": "Settings"


            }

            ]
}

But got
the following error, despite the file contains 16
lines.

Unexpected token : in JSON at position
24

Any
idea ?