winston logger: duplicate lines of same information logged

const winston = requires('winston');

const logDir = "./logs/";

function filePath(prefix) {

// get date time for file name
let today = new Date();
let dd = today.getDate();
let mm = today.getMonth() + 1; //January is 0!
let yyyy = today.getFullYear();

if (dd < 10) { dd = '0' + dd; }
if (mm < 10) { mm = '0' + mm; }

// file name format: mm_dd_yyyy_type
let name = mm + '_' + dd + '_' + yyyy + '_' + prefix + '_logs.txt';
let path = logDir + prefix + "-logs/" + name;
return path;
}

const { combine, timestamp, printf } = winston.format;
const logFormat = printf(info => {
      return `${info.timestamp} ${info.level}: ${info.message}`
});

let infoLogger = winston.createLogger({
format: combine(
    timestamp(),
    logFormat
  ),    
exitOnError: false 
});

let info = function (data) {

let infoDir = logDir + "info-logs/";
// create the info log directory if it does not exist
if (!file.existsSync(infoDir)) file.mkdirSync(infoDir);

const fileTransport = new winston.transports.File({
    level: "info",
    filename: filePath("info"),
    handleExceptions: true,
    json: true,
});
infoLogger.add(fileTransport);
infoLogger.info(data);
}

this is the code I am using. On my front end I have a form, which sends a request to backend. In the request handler this snippet of code executes:

const logger = require("../logger");
logger.info("some info logged");

when the server is fired. upon the first request, one line is logged correctly

2018-07-11T03:36:24.502Z info: some info logged

However, after say sending the request for the third time, this is the results

2018-07-11T03:36:24.502Z info: some info logged
2018-07-11T03:36:28.502Z info: some info logged
2018-07-11T03:36:28.502Z info: some info logged
2018-07-11T03:36:35.502Z info: some info logged
2018-07-11T03:36:35.502Z info: some info logged
2018-07-11T03:36:35.502Z info: some info logged

As you can notice, the information logged are multiplied according to number of request, ie on third request, three lines were appended to file.

Cannot seem to figure out the issue :/