implement cancellableSleep, so that obfsvpn clients in hopping mode stop...

implement cancellableSleep, so that obfsvpn clients in hopping mode stop quicker after Stop() was called. This is especially useful in case obfsvpn is integrated as a library to ensure correct state handling in fast reconnection scenarios e.g. after settings changes

client/client.go

@@ -302,25 +302,38 @@ func (c *Client) connectObfs4(obfs4Endpoint *Obfs4Config, sleepSeconds int) {
 		// If we wait sleepSeconds here to clean up the previous connection, we can guarantee that the
 		// connection list will not grow unbounded
 		go func() {
-			time.Sleep(time.Duration(sleepSeconds) * time.Second)
-
+			cancelled := cancellableSleep(c.ctx, time.Duration(sleepSeconds)*time.Second)
+			if cancelled {
+				c.log("Sleep for connection cleanup cancelled. Immediately cleaning up old connections")
+			}
 			c.cleanupOldConn()
 		}()
 	}
 }
 
+// cancellableSleep simulates a sleep that can be canceled by a context.
+func cancellableSleep(ctx context.Context, duration time.Duration) bool {
+	timer := time.NewTimer(duration)
+	defer timer.Stop()
+
+	select {
+	case <-timer.C:
+		return false // Sleep completed
+	case <-ctx.Done():
+		return true // Sleep canceled
+	}
+}
+
 func (c *Client) hop() {
 	for {
-		select {
-		case <-c.ctx.Done():
-			return
-		default:
-		}
-
 		// #nosec G404
 		sleepSeconds := rand.Intn(int(c.hopJitter)) + int(c.minHopSeconds)
 		c.log("Sleeping %d seconds...", sleepSeconds)
-		time.Sleep(time.Duration(sleepSeconds) * time.Second)
+		cancelled := cancellableSleep(c.ctx, time.Duration(sleepSeconds)*time.Second)
+		if cancelled {
+			c.log("Hop sleep cancelled")
+			return
+		}
 
 		obfs4Endpoint := c.pickRandomEndpoint()