Fail to start when on node v12

[Thesephi]

Reproduction:

• use Node.js v12 (e.g. nvm use v12)
• start the validator node with npm start
• run into this:

npm start

> oracle-validator-node@2.1.0 start
> npm run build && node 'dist/src/main.js' start


> oracle-validator-node@2.1.0 build
> tsc -p .

/home/ubuntu/fluxprotocol/oracle-validator-node/dist/src/config.js:20
exports.DB_PATH = process.env.DB_PATH ?? './';
                                       ^

SyntaxError: Unexpected token '?'

Recommended action: adjust tsc build config so that the nullish coalescing operator (??) is supported.

[t-moennich]

@Thesephi this is currently not possible, because the package @fluxprotocol/oracle-provider-near itself isn't compatible with node v12.
It's just getting transpiled with tsc using "target": "esnext", which allows the nullish coalescing operator.

You may use the CLI tool are-you-es5 to test this

To fix this, it's required to use a bundler like webpack or babel which also supports transpiling some of the used libraries.
If you would agree with that, I'll integrate webpack using ts-loader to support the current transpilation.

[Thesephi]

Hi @t-moennich, I would absolutely agree with that. In fact it's the initial reason why I created this issue. I had planned to propose this approach & contribute a small PR for it myself, but haven't got the needed time to do so :) So, if you'll do it, I'll happily help review it, but otherwise I'll do it in due time, and hopefully you or someone could help me review it. Either way, thank you so, so much for your time & considerations on this issue! 🙏

[t-moennich]

@Thesephi just FYI I can't finish it currently and doesn't get the node v12 compatibly to work.
This fails due multiple incompatibilities in different packages, there each would need a separate workaround during webpack processing.

As node v14 is getting LTS the amount of effort isn't worth IMHO.

If you agree, I'll update my branch to use webpack and create an ES6 bundle, working with node v14 and above.
If for some reason v12 support us really required, I'll create a WIP PR with my current state so anybody can try to finish it 😊