Fix race on deadman timer Elapsed+Reset by more efficient use of tick…

…er and ping time channel. Remove deadman file as it is no longer needed

socketmode/socket_mode_managed_conn.go

@@ -56,13 +56,12 @@ func (smc *Client) RunContext(ctx context.Context) error {
 func (smc *Client) run(ctx context.Context, connectionCount int) error {
 	messages := make(chan json.RawMessage, 1)
 
-	// FIXME: Race on "deadmanTimer", timer channel cannot be read concurrently while resetting.
-	// "This should not be done concurrent to other receives from the Timer's channel."
-	// https://pkg.go.dev/time#Timer.Reset
-	// See deadman.go line ~22.
-	deadmanTimer := newDeadmanTimer(smc.maxPingInterval)
+	pingChan := make(chan time.Time, 1)
 	pingHandler := func(_ string) error {
-		deadmanTimer.Reset()
+		select {
+		case pingChan <- time.Now():
+		default:
+		}
 
 		return nil
 	}
@@ -138,26 +137,44 @@ func (smc *Client) run(ctx context.Context, connectionCount int) error {
 	}()
 
 	wg.Add(1)
-	go func() {
+	go func(pingInterval time.Duration) {
 		defer wg.Done()
-
-		select {
-		case <-ctx.Done():
+		defer func() {
 			// Detect when the connection is dead and try close connection.
 			if err := conn.Close(); err != nil {
 				smc.Debugf("Failed to close connection: %v", err)
 			}
+		}()
+
+		done := ctx.Done()
+		var lastPing time.Time
+
+		// More efficient than constantly resetting a timer w/ Stop+Reset
+		ticker := time.NewTicker(pingInterval)
+		defer ticker.Stop()
 
-		// FIXME: Race on "deadmanTimer", timer channel cannot be read concurrently while resetting.
-		// "This should not be done concurrent to other receives from the Timer's channel."
-		// https://pkg.go.dev/time#Timer.Reset
-		// See deadman.go line ~22.
-		case <-deadmanTimer.Elapsed():
-			sendErr(errors.New("ping timeout: Slack did not send us WebSocket PING for more than Client.maxInterval"))
+		for {
+			select {
+			case <-done:
+				return
 
-			cancel()
+			case lastPing = <-pingChan:
+				// This case gets the time of the last ping.
+				// If this case never fires then the pingHandler was never called
+				// in which case lastPing is the zero time.Time value, and will 'fail'
+				// the next tick, causing us to exit.
+
+			case now := <-ticker.C:
+				// Our last ping is older than our interval
+				if now.Sub(lastPing) > pingInterval {
+					sendErr(errors.New("ping timeout: Slack did not send us WebSocket PING for more than Client.maxInterval"))
+
+					cancel()
+					return
+				}
+			}
 		}
-	}()
+	}(smc.maxPingInterval)
 
 	wg.Wait()
 
@@ -294,12 +311,13 @@ func (smc *Client) openAndDial(ctx context.Context, additionalPingHandler func(s
 		smc.Debugf("Failed to dial to the websocket: %s", err)
 		return nil, nil, err
 	}
+	if additionalPingHandler == nil {
+		additionalPingHandler = func(_ string) error { return nil }
+	}
 
 	conn.SetPingHandler(func(appData string) error {
-		if additionalPingHandler != nil {
-			if err := additionalPingHandler(appData); err != nil {
-				return err
-			}
+		if err := additionalPingHandler(appData); err != nil {
+			return err
 		}
 
 		smc.handlePing(conn, appData)