Struct InnerFuture

ch04/future.go:29–37

}

type InnerFuture struct {
	once sync.Once
	wg   sync.WaitGroup

	res   string
	err   error
	resCh <-chan string
	errCh <-chan error
}

func (f *InnerFuture) Result() (string, error) {
	f.once.Do(func() {