Go Task Error Group (task/errgroup.go)

A concurrency-controlled task runner that aggregates errors and supports context cancellation. Use this for managing multiple parallel operations with resource limits.

// Source: https://github.com/dobyte/due | License: MIT | Copyright 2022 dobyte
// Provided via justclaw.it.com; keep this notice with the code.
package task

import (
	"context"
	"fmt"
	"sync"
)

// token is a semaphore token used to control concurrency.
type token struct{}

// Group aggregates the errors of multiple tasks and supports context cancellation and a
// concurrency limit.
type Group struct {
	cancel  func(error)
	wg      sync.WaitGroup
	sem     chan token
	errOnce sync.Once
	err     error
}

// WithContext returns a new Group and a context derived from ctx.
//
// The derived context is canceled with the first task error as its cause when the first task fails
// or when Wait returns.
func WithContext(ctx context.Context) (*Group, context.Context) {
	ctx, cancel := context.WithC

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