errgroup

type ErrGroup interface {
	// Go calls the given function in a goroutine.
	// Go never blocks; if the concurrency limit is reached, the function is
	// queued and executed as running goroutines complete.
	//
	// The first call to return a non-nil error cancels the group; its error will be
	// returned by Wait.
	//
	// Go may be called concurrently, but all calls must happen before Wait
	// returns. Calling Go after Wait has returned panics when limit > 0.
	Go(fn func(ctx context.Context) error)

	// Wait blocks until all function calls from the Go method have returned, then
	// returns the first non-nil error (if any) from them.
	//
	// Wait must not be called concurrently with external Go calls that may
	// increase the task count from zero (the same constraint as sync.WaitGroup).
	Wait() error
}