on deploying meanapp , mongodb is working fine on local node server.js but when i deploy to heroku it showing error
2019-06-04T02:49:12.401001+00:00 heroku[web.1]: State changed from up to starting
2019-06-04T02:49:13.706279+00:00 heroku[web.1]: Stopping all processes with SIGTERM
2019-06-04T02:49:13.800926+00:00 heroku[web.1]: Process exited with status 143
2019-06-04T02:49:17.993509+00:00 heroku[web.1]: Starting process with command
node server.js2019-06-04T02:49:20.786431+00:00 app[web.1]: mongodb+srv://username:[email protected]
/test?retryWrites=true 2019-06-04T02:49:20.803912+00:00 app[web.1]: app listening at 40970
2019-06-04T02:49:20.972565+00:00 app[web.1]: database error MongoNetworkError: connection 4 to cluster0-shard-00-01-dlcak.mongodb.net:27017 closed
2019-06-04T02:49:20.973723+00:00 app[web.1]: (node:4) UnhandledPromiseRejectionWarning: TypeError: callback is not a function
2019-06-04T02:49:20.973725+00:00 app[web.1]: at $initialConnection.$initialConnection.then (/app/node_modules/mongoose/lib/connection.js:638:13)
2019-06-04T02:49:20.973810+00:00 app[web.1]: (node:4) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
2019-06-04T02:49:20.973880+00:00 app[web.1]: (node:4) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
2019-06-04T02:49:21.758205+00:00 heroku[web.1]: State changed from starting to up
