Override globalRegistry

I am trying to export metrics on file and then export it using other worker to metric collector.
right now, I have to pass file register in each metrics manually to get them to dump in file. forgetting that might lead to loosing those metrics.

So, is there anyway to override globalRegistry in code so that all metrics goes in file register by default instead of global default register ?

Full code snippet i am trying to use:

const fs = require('fs');
const path = require('path');
const { promisify } = require('util');
const client = require('prom-client');
const Registry = client.Registry;

class FileRegistry extends Registry {

    constructor(opts) {
        opts = opts || {};
        opts.metricsDir = opts.metricsDir || './metrics.pom';
        opts.saveInterval = opts.saveInterval || 4000; // in ms
        super();
        this.fileOpts = opts;
        this.startFlushLoop();
    }

    startFlushLoop() {
        setInterval(() => {
            this.writeToFile();
        }, this.fileOpts.saveInternal);
    }

    writeToFile() {
        const { metricsDir } = this.fileOpts;
        const pomStr = this.metrics();
        this.resetMetrics();
        console.log('pomStr', pomStr);
        appendFileAsync(metricsDir, pomStr, { flags: 'a+' })
            .catch(err => {
               // something really bad happened 
                console.error(err);
                process.exit(1);
            });

    }
}

// Current possible solution
const fileRegister = new FileRegistry();
const counter = new client.Counter({
    name: 'metric_name',
    help: 'metric_help',
    registers: [fileRegister]
});

Start by tracing the client.Registry/globalRegistry behavior and the client.Counter construction shown in the issue, then examine how registers are selected when none are supplied. Done means the supported approach lets metrics use the file registry by default without manually passing it to every metric, with behavior documented and covered by relevant tests.