errgroup

Structured concurrency for Node.js inspired by Go's errgroup, built on top of go-like-ctx. It does not replace ctx; it orchestrates it.

Install

npm install errgroup go-like-ctx

Usage

import { errgroup } from "errgroup";
import { background } from "go-like-ctx";

const ctx = background().withTimeout(5_000);
const g = errgroup(ctx, {
  onError(err) {
    console.error("register failed", err);
  }
});

g.go(async (ctx) => {
  await taskA(ctx);
});

g.go(async (ctx) => {
  await taskB(ctx);
});

try {
  await g.wait();
} finally {
  ctx.cancel();
}

If you want to observe errors without throwing, use waitSafe().

const res = await g.waitSafe();
if (!res.ok) {
  console.error("task failed", res.error);
}

Behavior

• Explicit context passing only.
• First error wins and cancels the shared context.
• Optional onError runs exactly once with the first error.
• Other tasks should observe ctx and exit early.
• wait() resolves after all tasks settle, then rethrows the first error.
• go() after wait() throws a usage error.

Example: Register endpoint

See examples/register.js for a more complete flow that verifies captcha, saves the user, subscribes them to email, sends a confirmation, and publishes analytics under a single context.

Why errgroup?

• One place to wait for all concurrent work.
• First error cancels the whole group to avoid wasted work.
• Forces structured, explicit context propagation (no globals).
• Keeps error handling consistent and predictable.

Development

npm install
npm run build
npm test
npm run test:watch