Update dependencies

vendor/github.com/tailscale/goupnp/httpu/multiclient.go

@@ -0,0 +1,72 @@
+package httpu
+
+import (
+	"net/http"
+
+	"golang.org/x/sync/errgroup"
+)
+
+// MultiClient dispatches requests out to all the delegated clients.
+type MultiClient struct {
+	// The HTTPU clients to delegate to.
+	delegates []ClientInterface
+}
+
+var _ ClientInterface = &MultiClient{}
+
+// NewMultiClient creates a new MultiClient that delegates to all the given
+// clients.
+func NewMultiClient(delegates []ClientInterface) *MultiClient {
+	return &MultiClient{delegates: delegates}
+}
+
+func (mc *MultiClient) Close() error {
+	for _, d := range mc.delegates {
+		d.Close()
+	}
+	return nil
+}
+
+// Do implements ClientInterface.Do.
+func (mc *MultiClient) Do(
+	req *http.Request,
+	numSends int,
+) ([]*http.Response, error) {
+	tasks := &errgroup.Group{}
+
+	results := make(chan []*http.Response)
+	tasks.Go(func() error {
+		defer close(results)
+		return mc.sendRequests(results, req, numSends)
+	})
+
+	var responses []*http.Response
+	tasks.Go(func() error {
+		for rs := range results {
+			responses = append(responses, rs...)
+		}
+		return nil
+	})
+
+	return responses, tasks.Wait()
+}
+
+func (mc *MultiClient) sendRequests(
+	results chan<- []*http.Response,
+	req *http.Request,
+	numSends int,
+) error {
+	tasks := &errgroup.Group{}
+	for _, d := range mc.delegates {
+		d := d // copy for closure
+		tasks.Go(func() error {
+			responses, err := d.Do(req, numSends)
+			if err != nil {
+				return err
+			}
+			results <- responses
+			return nil
+		})
+	}
+	return tasks.Wait()
+}