net/http: make CloseNotifier channel buffered to not leak goroutines

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/8911044

src/pkg/net/http/serve_test.go

@@ -1370,6 +1370,7 @@ func TestContentLengthZero(t *testing.T) {
 }
 
 func TestCloseNotifier(t *testing.T) {
+	defer afterTest(t)
 	gotReq := make(chan bool, 1)
 	sawClose := make(chan bool, 1)
 	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, req *Request) {
@@ -1405,6 +1406,31 @@ For:
 	ts.Close()
 }
 
+func TestCloseNotifierChanLeak(t *testing.T) {
+	defer afterTest(t)
+	req := []byte(strings.Replace(`GET / HTTP/1.0
+Host: golang.org
+
+`, "\n", "\r\n", -1))
+	for i := 0; i < 20; i++ {
+		var output bytes.Buffer
+		conn := &rwTestConn{
+			Reader: bytes.NewReader(req),
+			Writer: &output,
+			closec: make(chan bool, 1),
+		}
+		ln := &oneConnListener{conn: conn}
+		handler := HandlerFunc(func(rw ResponseWriter, r *Request) {
+			// Ignore the return value and never read from
+			// it, testing that we don't leak goroutines
+			// on the sending side:
+			_ = rw.(CloseNotifier).CloseNotify()
+		})
+		go Serve(ln, handler)
+		<-conn.closec
+	}
+}
+
 func TestOptions(t *testing.T) {
 	uric := make(chan string, 2) // only expect 1, but leave space for 2
 	mux := NewServeMux()

src/pkg/net/http/server.go

@@ -146,7 +146,7 @@ func (c *conn) closeNotify() <-chan bool {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	if c.closeNotifyc == nil {
-		c.closeNotifyc = make(chan bool)
+		c.closeNotifyc = make(chan bool, 1)
 		if c.hijackedv {
 			// to obey the function signature, even though
 			// it'll never receive a value.

src/pkg/net/http/z_last_test.go

@@ -76,6 +76,7 @@ func afterTest(t *testing.T) {
 		"created by net/http/httptest.(*Server).Start": "an httptest.Server",
 		"timeoutHandler":                               "a TimeoutHandler",
 		"net.(*netFD).connect(":                        "a timing out dial",
+		").noteClientGone(":                            "a closenotifier sender",
 	}
 	var stacks string
 	for i := 0; i < 4; i++ {