Comparison to Our Original Approach

 1package main
 2
 3import "context"
 4
 5type Group struct {
 6	errc   chan error
 7	cancel context.CancelCauseFunc
 8	count  int
 9}
10
11func NewGroup(cancel context.CancelCauseFunc) *Group {
12	return &Group{errc: make(chan error, 1), cancel: cancel}
13}
14
15func (g *Group) Go(f func() error) {
16	g.count++
17	go func() {
18		g.errc <- f()
19	}()
20}
21
22func (g *Group) Wait() error {
23	var err error
24	for range g.count {
25		if e := <-g.errc; e != nil && err == nil {
26			err = e
27			g.cancel(e)
28		}
29	}
30
31	return err
32}

 1package main
 2
 3import (
 4	"context"
 5
 6	"fillmore-labs.com/blog/structured/pkg/task"
 7)
 8
 9func doWork(ctx context.Context) error {
10	ctx, cancel := context.WithCancelCause(ctx)
11	defer cancel(nil)
12
13	g := NewGroup(cancel)
14
15	g.Go(func() error {
16		return task.Task(ctx, "task1", processingTime/3, nil)
17	})
18
19	g.Go(func() error {
20		return task.Task(ctx, "task2", processingTime/2, errFail)
21	})
22
23	g.Go(func() error {
24		return task.Task(ctx, "task3", processingTime, nil)
25	})
26
27	return g.Wait()
28}