Source: errgroup.go in package golang.org/x/sync/errgroup

Source File
	errgroup.go

Belonging Package
	golang.org/x/sync/errgroup

Package errgroup provides synchronization, error propagation, and Context cancelation for groups of goroutines working on subtasks of a common task.

package errgroup

import (
	"context"
	"sync"
)

A Group is a collection of goroutines working on subtasks that are part of the same overall task. A zero Group is valid and does not cancel on error.

type Group struct {
	cancel func()

	wg sync.WaitGroup

	errOnce sync.Once
	err     error
}

WithContext returns a new Group and an associated Context derived from ctx. The derived Context is canceled the first time a function passed to Go returns a non-nil error or the first time Wait returns, whichever occurs first.

func WithContext(ctx context.Context) (*Group, context.Context) {
	ctx, cancel := context.WithCancel(ctx)
	return &Group{cancel: cancel}, ctx
}

Wait blocks until all function calls from the Go method have returned, then returns the first non-nil error (if any) from them.

func (g *Group) Wait() error {
	g.wg.Wait()
	if g.cancel != nil {
		g.cancel()
	}
	return g.err
}

Go calls the given function in a new goroutine. The first call to return a non-nil error cancels the group; its error will be returned by Wait.

func (g *Group) Go(f func() error) {
	g.wg.Add(1)

	go func() {
		defer g.wg.Done()

		if err := f(); err != nil {
			g.errOnce.Do(func() {
				g.err = err
				if g.cancel != nil {
					g.cancel()
				}
			})
		}
	}()


The pages are generated with Golds v0.3.2-preview. (GOOS=darwin GOARCH=amd64)
Golds is a Go 101 project developed by Tapir Liu.
PR and bug reports are welcome and can be submitted to the issue list.
Please follow @Go100and1 (reachable from the left QR code) to get the latest news of Golds.