Hi,
I've hit a really weird corner case when node-geolite2 is used with Meteor.js. Meteor requires users to perform a post-build step in the application bundle directory - here's a snippet from the README file it creates:

$ (cd programs/server && npm install) 

This, in turn, launches npm-rebuild.js, which goes into several sub-directories (notably npm/) and does npm install in them. This is all quite complex, but the end result is: it launches npm install, in a directory (cwd) which has no package.json file. This throws, even though the MAXMIND_LICENSE_KEY environment variable is set:

Error: Cannot find module '<some_meteor_bundle_dir>/programs/server/npm/package.json' Require stack: - <some_meteor_bundle_dir>/programs/server/npm/node_modules/geolite2/utils.js - <some_meteor_bundle_dir>/programs/server/npm/node_modules/geolite2/scripts/postinstall.js at Function.Module._resolveFilename (internal/modules/cjs/loader.js:815:15) at Function.Module._load (internal/modules/cjs/loader.js:667:27) at Module.require (internal/modules/cjs/loader.js:887:19) at require (internal/modules/cjs/helpers.js:74:18) at getConfig (<some_meteor_bundle_dir>/programs/server/npm/node_modules/geolite2/utils.js:9:23) at getSelectedDbs (<some_meteor_bundle_dir>/programs/server/npm/node_modules/geolite2/utils.js:31:18) at Object.<anonymous> (<some_meteor_bundle_dir>/programs/server/npm/node_modules/geolite2/scripts/postinstall.js:38:18) at Module._compile (internal/modules/cjs/loader.js:999:30) at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10) at Module.load (internal/modules/cjs/loader.js:863:32) { code: 'MODULE_NOT_FOUND', requireStack: [ '<some_meteor_bundle_dir>/programs/server/npm/node_modules/geolite2/utils.js', '<some_meteor_bundle_dir>/programs/server/npm/node_modules/geolite2/scripts/postinstall.js' ] } 

As far as I can tell, prior to PR #34, this library had a list of configuration loaders which would run one-by-one, so if the env variable was enough, we never tried to require() the package.json file. However, #34 broke this - now, the postinstall script blindly tries to find the file, and fails - since the file does not exist in the current working directory.

This results in post-build failures of Meteor application bundles for applications that have geolite2 as a dependency. The current work-around seems to be setting METEOR_SKIP_NPM_REBUILD=1 (which limits deployment options, really). The problem's scope is not limited to Meteor - anything that tries to do an npm install in a CWD without a package.json will fail in the same way.

A solution could be to gracefully recover from a missing config and assume some defaults w.r.t. which databases the user wants. This would restore the previous behavior (pre #34), where MAXMIND_LICENSE_KEY was enough to use this package.