lwk: set prime seconds

This way, it prevents many automated clients from attacking
the server at the same time.
For example, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79,
83, 89 and 97 are good numbers.

lwk/electrumtxwatcher.go

@@ -16,7 +16,10 @@ const (
 	// initialBlockHeaderSubscriptionTimeout is
 	// the initial block header subscription timeout.
 	initialBlockHeaderSubscriptionTimeout = 1000 * time.Second
-	blockHeaderSubscriptionTicker         = 30 * time.Second
+	// Set prime seconds.
+	// This way, it prevents many automated clients from attacking the server at the same time.
+	// For example, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89 and 97 are good numbers.
+	blockHeaderSubscriptionTicker = 37 * time.Second
 )
 
 type electrumTxWatcher struct {