http2: only set up deadline when Server.IdleTimeout is positive

Check out https://go-review.googlesource.com/c/go/+/570396

Change-Id: I8bda17acebc27308c2a1723191ea1e4a9e64d585
Reviewed-on: https://go-review.googlesource.com/c/net/+/570455
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
Auto-Submit: Damien Neil <dneil@google.com>

http2/server.go

@@ -124,6 +124,7 @@ type Server struct {
 	// IdleTimeout specifies how long until idle clients should be
 	// closed with a GOAWAY frame. PING frames are not considered
 	// activity for the purposes of IdleTimeout.
+	// If zero or negative, there is no timeout.
 	IdleTimeout time.Duration
 
 	// MaxUploadBufferPerConnection is the size of the initial flow
@@ -924,7 +925,7 @@ func (sc *serverConn) serve() {
 	sc.setConnState(http.StateActive)
 	sc.setConnState(http.StateIdle)
 
-	if sc.srv.IdleTimeout != 0 {
+	if sc.srv.IdleTimeout > 0 {
 		sc.idleTimer = time.AfterFunc(sc.srv.IdleTimeout, sc.onIdleTimer)
 		defer sc.idleTimer.Stop()
 	}
@@ -1637,7 +1638,7 @@ func (sc *serverConn) closeStream(st *stream, err error) {
 	delete(sc.streams, st.id)
 	if len(sc.streams) == 0 {
 		sc.setConnState(http.StateIdle)
-		if sc.srv.IdleTimeout != 0 {
+		if sc.srv.IdleTimeout > 0 {
 			sc.idleTimer.Reset(sc.srv.IdleTimeout)
 		}
 		if h1ServerKeepAlivesDisabled(sc.hs) {