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How to reproduce

The problem

Hi I’m trying to gzip some files in a .then() promise chain so I tried using gzipAsync() but received the following error:

Error: async operations unsupported - update to Node 12+ (or Node 10-11 with the --experimental-worker CLI flag)
    at Immediate.<anonymous> (file:///home/today/_/work/haptic/node_modules/fflate/esm/index.mjs:34:42)
    at processImmediate (internal/timers.js:456:21)

I’m running Node v14.2.0. The file is ESM via "type": "module" in package.json. The file imports fflate like this:

import esbuild from 'esbuild';
import { gzip, gzipSync } from 'fflate';
import { readFile, writeFile } from 'fs/promises';
// ...

Here’s the code that throws on L47:

If I replace L47 with res(gzipSync(readData, { consume: true, level: 9 })); then it’s fine. It’s also fast enough that I’m not reporting an issue with Sync vs Async, just that the error message might be wrong if it’s telling people to update to 12+.

Thanks!