Error: Cannot find module './formats' on deplying to herkou or digitalocean

I have a nodejs + mongodb app and it works properly on my local machine but I'm facing a problem in deployment here are the logs from heroku

2017-05-29T22:14:21.706635+00:00 heroku[web.1]: Starting process with command `node server.js`
    2017-05-29T22:14:23.859502+00:00 app[web.1]: module.js:471
    2017-05-29T22:14:23.859516+00:00 app[web.1]:     throw err;
    2017-05-29T22:14:23.859517+00:00 app[web.1]:     ^
    2017-05-29T22:14:23.859517+00:00 app[web.1]: 
    2017-05-29T22:14:23.859518+00:00 app[web.1]: Error: Cannot find module './formats'
    2017-05-29T22:14:23.859519+00:00 app[web.1]:     at Function.Module._resolveFilename (module.js:469:15)
    2017-05-29T22:14:23.859520+00:00 app[web.1]:     at Function.Module._load (module.js:417:25)
    2017-05-29T22:14:23.859521+00:00 app[web.1]:     at Module.require (module.js:497:17)
    2017-05-29T22:14:23.859521+00:00 app[web.1]:     at require (internal/module.js:20:19)
    2017-05-29T22:14:23.859522+00:00 app[web.1]:     at Object.<anonymous> (/app/node_modules/qs/lib/stringify.js:4:15)
    2017-05-29T22:14:23.859523+00:00 app[web.1]:     at Module._compile (module.js:570:32)
    2017-05-29T22:14:23.859524+00:00 app[web.1]:     at Object.Module._extensions..js (module.js:579:10)
    2017-05-29T22:14:23.859524+00:00 app[web.1]:     at Module.load (module.js:487:32)
    2017-05-29T22:14:23.859525+00:00 app[web.1]:     at tryModuleLoad (module.js:446:12)
    2017-05-29T22:14:23.859526+00:00 app[web.1]:     at Function.Module._load (module.js:438:3)
    2017-05-29T22:14:23.924630+00:00 heroku[web.1]: Process exited with status 1
    2017-05-29T22:14:23.941072+00:00 heroku[web.1]: State changed from starting to crashed
    2017-05-29T22:15:19.924922+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=dry-river-85545.herokuapp.com request_id=a28024a6-676e-4f33-88fe-37475038373f fwd="197.166.171.187" dyno= connect= service= status=503 bytes= protocol=https
    2017-05-29T22:15:23.327025+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=dry-river-85545.herokuapp.com request_id=2b86cf88-9f46-4f6f-95d7-8462ce2c8230 fwd="197.166.171.187" dyno= connect= service= status=503 bytes= protocol=https