net/http: use runtime.AddCleanup instead of runtime.SetFinalizer

Replace the usage of runtime.SetFinalizer with runtime.AddCleanup in
tests.

Updates #70907

Change-Id: Idd3f1c07f6a7709352ca09948fbcb4a0ad9418bb
Reviewed-on: https://go-review.googlesource.com/c/go/+/648655
Auto-Submit: Carlos Amedee <carlos@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

Author: cagedmantis

src/net/http/clientserver_test.go

@@ -1253,7 +1253,7 @@ func testTransportGCRequest(t *testing.T, mode testMode, body bool) {
 	(func() {
 		body := strings.NewReader("some body")
 		req, _ := NewRequest("POST", cst.ts.URL, body)
-		runtime.SetFinalizer(req, func(*Request) { close(didGC) })
+		runtime.AddCleanup(req, func(ch chan struct{}) { close(ch) }, didGC)
 		res, err := cst.c.Do(req)
 		if err != nil {
 			t.Fatal(err)

src/net/http/transport_test.go

@@ -2034,7 +2034,7 @@ func (d *countingDialer) DialContext(ctx context.Context, network, address strin
 	d.total++
 	d.live++
 
-	runtime.SetFinalizer(counted, d.decrement)
+	runtime.AddCleanup(counted, func(dd *countingDialer) { dd.decrement(nil) }, d)
 	return counted, nil
 }
 
@@ -2106,7 +2106,7 @@ func (cc *contextCounter) Track(ctx context.Context) context.Context {
 	cc.mu.Lock()
 	defer cc.mu.Unlock()
 	cc.live++
-	runtime.SetFinalizer(counted, cc.decrement)
+	runtime.AddCleanup(counted, func(c *contextCounter) { cc.decrement(nil) }, cc)
 	return counted
 }