$ cd app/auth
$ npm install --save express-validator

$ curl \
--data '{"email":"notValidEmail", "password":"1"}' \
--header "Content-Type: application/json" \
--request POST http:https://adi-ticketing.dev/api/users/signup \
| python -m json.tool

[
    {
        "location": "body",
        "msg": "Email must be valid",
        "param": "email",
        "value": "notValidEmail"
    },
    {
        "location": "body",
        "msg": "Password must be between 4 and 20 characters",
        "param": "password",
        "value": "1"
    }
]

$ cd app/auth
$ npm install --save express-async-errors