refactor: use context.AfterFunc to track timeouts instead of goroutine (#532)

Closes #411
Closes #501

Author: ash2k

close.go

@@ -231,12 +231,6 @@ func (c *Conn) waitGoroutines() error {
 	t := time.NewTimer(time.Second * 15)
 	defer t.Stop()
 
-	select {
-	case <-c.timeoutLoopDone:
-	case <-t.C:
-		return errors.New("failed to wait for timeoutLoop goroutine to exit")
-	}
-
 	c.closeReadMu.Lock()
 	closeRead := c.closeReadCtx != nil
 	c.closeReadMu.Unlock()

conn.go

@@ -51,9 +51,8 @@ type Conn struct {
 	br             *bufio.Reader
 	bw             *bufio.Writer
 
-	readTimeout     chan context.Context
-	writeTimeout    chan context.Context
-	timeoutLoopDone chan struct{}
+	readTimeoutStop  atomic.Pointer[func() bool]
+	writeTimeoutStop atomic.Pointer[func() bool]
 
 	// Read state.
 	readMu         *mu
@@ -113,10 +112,6 @@ func newConn(cfg connConfig) *Conn {
 		br: cfg.br,
 		bw: cfg.bw,
 
-		readTimeout:     make(chan context.Context),
-		writeTimeout:    make(chan context.Context),
-		timeoutLoopDone: make(chan struct{}),
-
 		closed:         make(chan struct{}),
 		activePings:    make(map[string]chan<- struct{}),
 		onPingReceived: cfg.onPingReceived,
@@ -144,8 +139,6 @@ func newConn(cfg connConfig) *Conn {
 		c.close()
 	})
 
-	go c.timeoutLoop()
-
 	return c
 }
 
@@ -175,27 +168,34 @@ func (c *Conn) close() error {
 	return err
 }
 
-func (c *Conn) timeoutLoop() {
-	defer close(c.timeoutLoopDone)
+func (c *Conn) setupWriteTimeout(ctx context.Context) {
+	stop := context.AfterFunc(ctx, func() {
+		c.clearWriteTimeout()
+		c.close()
+	})
+	swapTimeoutStop(&c.writeTimeoutStop, &stop)
+}
 
-	readCtx := context.Background()
-	writeCtx := context.Background()
+func (c *Conn) clearWriteTimeout() {
+	swapTimeoutStop(&c.writeTimeoutStop, nil)
+}
 
-	for {
-		select {
-		case <-c.closed:
-			return
-
-		case writeCtx = <-c.writeTimeout:
-		case readCtx = <-c.readTimeout:
-
-		case <-readCtx.Done():
-			c.close()
-			return
-		case <-writeCtx.Done():
-			c.close()
-			return
-		}
+func (c *Conn) setupReadTimeout(ctx context.Context) {
+	stop := context.AfterFunc(ctx, func() {
+		c.clearReadTimeout()
+		c.close()
+	})
+	swapTimeoutStop(&c.readTimeoutStop, &stop)
+}
+
+func (c *Conn) clearReadTimeout() {
+	swapTimeoutStop(&c.readTimeoutStop, nil)
+}
+
+func swapTimeoutStop(p *atomic.Pointer[func() bool], newStop *func() bool) {
+	oldStop := p.Swap(newStop)
+	if oldStop != nil {
+		(*oldStop)()
 	}
 }
 

read.go

@@ -220,22 +220,24 @@ func (c *Conn) readLoop(ctx context.Context) (header, error) {
 // to be called after the read is done. It also returns an error if the
 // connection is closed. The reference to the error is used to assign
 // an error depending on if the connection closed or the context timed
-// out during use. Typically the referenced error is a named return
+// out during use. Typically, the referenced error is a named return
 // variable of the function calling this method.
 func (c *Conn) prepareRead(ctx context.Context, err *error) (func(), error) {
 	select {
 	case <-c.closed:
 		return nil, net.ErrClosed
-	case c.readTimeout <- ctx:
+	default:
 	}
+	c.setupReadTimeout(ctx)
 
 	done := func() {
+		c.clearReadTimeout()
 		select {
 		case <-c.closed:
 			if *err != nil {
 				*err = net.ErrClosed
 			}
-		case c.readTimeout <- context.Background():
+		default:
 		}
 		if *err != nil && ctx.Err() != nil {
 			*err = ctx.Err()
@@ -280,7 +282,7 @@ func (c *Conn) readFramePayload(ctx context.Context, p []byte) (_ int, err error
 		return n, fmt.Errorf("failed to read frame payload: %w", err)
 	}
 
-	return n, err
+	return n, nil
 }
 
 func (c *Conn) handleControl(ctx context.Context, h header) (err error) {

write.go

@@ -271,14 +271,10 @@ func (c *Conn) writeFrame(ctx context.Context, fin bool, flate bool, opcode opco
 	select {
 	case <-c.closed:
 		return 0, net.ErrClosed
-	case c.writeTimeout <- ctx:
+	default:
 	}
-	defer func() {
-		select {
-		case <-c.closed:
-		case c.writeTimeout <- context.Background():
-		}
-	}()
+	c.setupWriteTimeout(ctx)
+	defer c.clearWriteTimeout()
 
 	c.writeHeader.fin = fin
 	c.writeHeader.opcode = opcode