Update golang dependencies

vendor/golang.org/x/net/context/ctxhttp/ctxhttp.go

@@ -27,7 +27,17 @@ func Do(ctx context.Context, client *http.Client, req *http.Request) (*http.Resp
 	if client == nil {
 		client = http.DefaultClient
 	}
-	return client.Do(req.WithContext(ctx))
+	resp, err := client.Do(req.WithContext(ctx))
+	// If we got an error, and the context has been canceled,
+	// the context's error is probably more useful.
+	if err != nil {
+		select {
+		case <-ctx.Done():
+			err = ctx.Err()
+		default:
+		}
+	}
+	return resp, err
 }
 
 // Get issues a GET request via the Do function.