Nest.js error with ENOENT: no such file or directory, open './push-service-account.json'

Looks like in your PushService you are trying to read ./push-service-account.json. This may look fine in your src directory, but when you compile, Typescript won't move the json file for you. You either need to use a post-build step that moves all .json files you plan to read to the relative dist location, or you should put all of these .json files in a common directory relative to your project root so that you can use fs.readFile(path.join(process.cwd(), 'common', fileName))