ax(node): rename ttl to timeToLive in MessageDeduplicator

AX Principle 1 — predictable names over short names.
The field `ttl` requires context to decode; `timeToLive` is
self-describing without a comment.

Co-Authored-By: Charon <charon@lethean.io>

pkg/node/transport.go

@@ -61,18 +61,18 @@ type MessageHandler func(conn *PeerConnection, msg *Message)
 // if dedup.IsDuplicate(msg.ID) { continue }
 // dedup.Mark(msg.ID)
 type MessageDeduplicator struct {
-	seen  map[string]time.Time
-	mutex sync.RWMutex
-	ttl   time.Duration
+	seen        map[string]time.Time
+	mutex       sync.RWMutex
+	timeToLive  time.Duration
 }
 
 // dedup := node.NewMessageDeduplicator(5 * time.Minute)
 // dedup.Mark(msg.ID)
 // if dedup.IsDuplicate(msg.ID) { continue }
-func NewMessageDeduplicator(ttl time.Duration) *MessageDeduplicator {
+func NewMessageDeduplicator(timeToLive time.Duration) *MessageDeduplicator {
 	deduplicator := &MessageDeduplicator{
-		seen: make(map[string]time.Time),
-		ttl:  ttl,
+		seen:       make(map[string]time.Time),
+		timeToLive: timeToLive,
 	}
 	return deduplicator
 }
@@ -92,13 +92,13 @@ func (deduplicator *MessageDeduplicator) Mark(msgID string) {
 	deduplicator.mutex.Unlock()
 }
 
-// go dedup.Cleanup() // call periodically; entries older than ttl are dropped
+// go dedup.Cleanup() // call periodically; entries older than timeToLive are dropped
 func (deduplicator *MessageDeduplicator) Cleanup() {
 	deduplicator.mutex.Lock()
 	defer deduplicator.mutex.Unlock()
 	now := time.Now()
 	for id, seen := range deduplicator.seen {
-		if now.Sub(seen) > deduplicator.ttl {
+		if now.Sub(seen) > deduplicator.timeToLive {
 			delete(deduplicator.seen, id)
 		}
 	}