resultCh := g.DoChan(key, func() (i interface{}, e error) {
		panic("third must not be started")
	})

	if g.ForgetUnshared(key) {
		t.Errorf("Before first goroutine finished, key %q is shared, should return false", key)
	}

	close(firstCh)
	firstFinished.Wait()

	if g.ForgetUnshared(key) {
		t.Errorf("After first goroutine finished, key %q is still shared, should return false", key)
	}

	g.mu.Lock()
	c.wg.Done()
	if g.m[key] == c {
		delete(g.m, key)
	}
	for _, ch := range c.chans {
		ch <- Result{c.val, c.err, c.dups > 0}
	}
	g.mu.Unlock()
}

// ForgetUnshared tells the singleflight to forget about a key if it is not
// shared with any other goroutines. Future calls to Do for a forgotten key
// will call the function rather than waiting for an earlier call to complete.

		// If there are other goroutines looking up this key,
		// let the lookup continue uncanceled, and let later
		// lookups with the same key share the result.
		// See issues 8602, 20703, 22724.
		if r.getLookupGroup().ForgetUnshared(lookupKey) {
			lookupGroupCancel()
			go dnsWaitGroupDone(ch, func() {})
		} else {
			go dnsWaitGroupDone(ch, lookupGroupCancel)
		}
		err := newDNSError(mapErr(ctx.Err()), host, "")