node structured logging configuration

logger.js

'use strict';

const winston = require('winston');
const MESSAGE = Symbol.for('message');

const jsonFormatter = (logEntry) => {
    const base = { timestamp: new Date() };
    const json = Object.assign(base, logEntry)
    logEntry[MESSAGE] = JSON.stringify(json);
    return logEntry;
};

exports.logger = winston.createLogger({
    format: winston.format(jsonFormatter)(),
    transports: new winston.transports.Console(),
});