errgroup: modernize the usage of closures in goroutines

Change-Id: I8b8a902fede0a77b11af130868dbf26b67c73ebf
Reviewed-on: https://go-review.googlesource.com/c/sync/+/836625
Reviewed-by: Alan Donovan <adonovan@google.com>
Reviewed-by: Mark Freeman <mark@golang.org>
Auto-Submit: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

errgroup/errgroup_test.go

diff --git a/errgroup/errgroup_test.go b/errgroup/errgroup_test.go
index 3b563af..92ac010 100644
--- a/errgroup/errgroup_test.go
+++ b/errgroup/errgroup_test.go
@@ -44,7 +44,6 @@
 	}
 	for _, url := range urls {
 		// Launch a goroutine to fetch the URL.
-		url := url // https://golang.org/doc/faq#closures_and_goroutines
 		g.Go(func() error {
 			// Fetch the URL.
 			resp, err := http.Get(url)
@@ -71,7 +70,6 @@
 		searches := []Search{Web, Image, Video}
 		results := make([]Result, len(searches))
 		for i, search := range searches {
-			i, search := i, search // https://golang.org/doc/faq#closures_and_goroutines
 			g.Go(func() error {
 				result, err := search(ctx, query)
 				if err == nil {
@@ -120,7 +118,6 @@
 
 		var firstErr error
 		for i, err := range tc.errs {
-			err := err
 			g.Go(func() error { return err })
 
 			if firstErr == nil && err != nil {
@@ -153,7 +150,6 @@
 		g, ctx := errgroup.WithContext(context.Background())
 
 		for _, err := range tc.errs {
-			err := err
 			g.Go(func() error { return err })
 		}
 
@@ -267,7 +263,6 @@
 		g, ctx := errgroup.WithContext(context.Background())
 
 		for _, err := range tc.errs {
-			err := err
 			g.TryGo(func() error { return err })
 		}