app.use(expressValidator({
    errorFormatter: function (param, msg, value) {
        let namespace = param.split('.'),
            root = namespace.shift(),
            formParam = root;

        while (namespace.length) {
            formParam += '[' + namespace.shift() + ']';
        }
        return {
            param: formParam,
            msg: msg,
            value: value
        };
    },

    customValidators: {
        isEmailAvailable(email) {
                let sql = "SELECT * FROM individual_users WHERE email = ?";
                let query = connection.query(sql,[email],(err,rows)=>{
                    if(err){
                        throw err;
                    }
                    if(rows.length >0){
                        return true;
                    } else {
                        return false;
                    }
                });
        }
    }
}));