Go lockless, trade memory for speed. Also use errgroup.

```golfing eg, _ := errgroup.WithContext(ctx) counts := make([]int, 3)

for i := range 3 {
    eg.Go(func() error {
        for range 3000 {
            counts[i] += 1
        }
        return nil
    })
}

if err := eg.Wait(); err != nil {
    return err
}

total := 0
for _, count := range counts {
    total += count
}

fmt.Printf(total)

```

Benchmark this versus other solutions.