User time.AfterFunc to remove the need of explicitly managing goroutines

The race in golang/go#11513 does not affect
time.AfterFunc, because the timer returned by time.AfterFunc() does not
have the buffered channel at all.

Author: Chao Xu

http2/transport.go

@@ -113,10 +113,12 @@ type Transport struct {
 	// if response is not received within PingTimeout.
 	// 0 means no periodic pings. Defaults to 0.
 	PingPeriod time.Duration
+
 	// PingTimeout is the timeout after which the connection will be closed
 	// if a response to Ping is not received.
 	// 0 means no periodic pings. Defaults to 0.
 	PingTimeout time.Duration
+
 	// ReadIdleTimeout is the timeout after which the periodic ping for
 	// connection health check will begin if no frame is received on the
 	// connection.
@@ -148,6 +150,14 @@ func (t *Transport) disableCompression() bool {
 	return t.DisableCompression || (t.t1 != nil && t.t1.DisableCompression)
 }
 
+func (t *Transport) readIdleTimeout() time.Duration {
+	to := t.ReadIdleTimeout
+	if to == 0 {
+		to = 60 * time.Second
+	}
+	return to
+}
+
 // ConfigureTransport configures a net/http HTTP/1 Transport to use HTTP/2.
 // It returns an error if t1 has already been HTTP/2-enabled.
 func ConfigureTransport(t1 *http.Transport) error {
@@ -1775,42 +1785,17 @@ func (rl *clientConnReadLoop) cleanup() {
 	cc.mu.Unlock()
 }
 
-type frameAndError struct {
-	f   Frame
-	err error
-}
-
-func nonBlockingReadFrame(fr *Framer) chan frameAndError {
-	feCh := make(chan frameAndError)
-	go func() {
-		f, err := fr.ReadFrame()
-		feCh <- frameAndError{f: f, err: err}
-	}()
-	return feCh
-}
-
 func (rl *clientConnReadLoop) run() error {
 	cc := rl.cc
 	rl.closeWhenIdle = cc.t.disableKeepAlives() || cc.singleUse
 	gotReply := false // ever saw a HEADERS reply
 	gotSettings := false
+	to := cc.t.readIdleTimeout()
+	t := time.AfterFunc(to, cc.startHealthCheck)
 	for {
-		var fe frameAndError
-		feCh := nonBlockingReadFrame(cc.fr)
-		to := cc.t.ReadIdleTimeout
-		if to == 0 {
-			to = 60 * time.Second
-		}
-		readIdleTimer := time.NewTimer(to)
-		select {
-		case fe = <-feCh:
-			cc.stopHealthCheck()
-			readIdleTimer.Stop()
-		case <-readIdleTimer.C:
-			cc.startHealthCheck()
-			fe = <-feCh
-		}
-		f, err := fe.f, fe.err
+		f, err := cc.fr.ReadFrame()
+		t.Reset(to)
+		cc.stopHealthCheck()
 		if err != nil {
 			cc.vlogf("http2: Transport readFrame error on conn %p: (%T) %v", cc, err, err)
 		}