errgroup

Documentation

Overview

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

errgroup.Group is related to sync.WaitGroup but adds handling of tasks returning errors.

Index

• type Group
  • func WithContext(ctx context.Context) (*Group, context.Context)
  • func (g *Group) Go(f func() error)
  • func (g *Group) SetLimit(n int)
  • func (g *Group) TryGo(f func() error) bool
  • func (g *Group) Wait() error

Types

type Group

type Group struct {
	// contains filtered or unexported fields
}

A Group is a collection of goroutines working on subtasks that are part of the same overall task.

A zero Group is valid, has no limit on the number of active goroutines, and does not cancel on error.

func WithContext

func WithContext(ctx context.Context) (*Group, context.Context)

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 (*Group) Go

func (g *Group) Go(f func() error)

Go calls the given function in a new goroutine. It blocks until the new goroutine can be added without the number of active goroutines in the group exceeding the configured limit.

The first call to return a non-nil error cancels the group's context, if the group was created by calling WithContext. The error will be returned by Wait.

func (*Group) SetLimit

func (g *Group) SetLimit(n int)

SetLimit limits the number of active goroutines in this group to at most n. A negative value indicates no limit.

Any subsequent call to the Go method will block until it can add an active goroutine without exceeding the configured limit.

The limit must not be modified while any goroutines in the group are active.

func (*Group) TryGo

func (g *Group) TryGo(f func() error) bool

TryGo calls the given function in a new goroutine only if the number of active goroutines in the group is currently below the configured limit.

The return value reports whether the goroutine was started.

func (*Group) Wait

func (g *Group) Wait() error

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