Don't close channels as receivers

In many places in the code, a receiver creates a channel, passes it to
the sender, and closes it on shutdown. This sometimes results in panics
due to sends on a closed channel, because the receiver oftentimes cannot
guarantee that the sender has stopped sending. In general, only the
sender should close channels, and only if necessary in order to notify
the receiver that no more elements are coming. To fix this, we just
remove the close statements as they are not needed.

Author: jannikluhn

rolling-shutter/keyperimpl/gnosis/keyper.go

@@ -73,10 +73,6 @@ func (kpr *Keyper) Start(ctx context.Context, runner service.Runner) error {
 	kpr.newKeyperSets = make(chan *syncevent.KeyperSet)
 	kpr.newEonPublicKeys = make(chan keyper.EonPublicKey)
 	kpr.decryptionTriggerChannel = make(chan *broker.Event[*epochkghandler.DecryptionTrigger])
-	runner.Defer(func() { close(kpr.newBlocks) })
-	runner.Defer(func() { close(kpr.newKeyperSets) })
-	runner.Defer(func() { close(kpr.newEonPublicKeys) })
-	runner.Defer(func() { close(kpr.decryptionTriggerChannel) })
 
 	kpr.latestTriggeredSlot = nil
 

rolling-shutter/medley/chainsync/syncer/eonpubkey.go

@@ -56,9 +56,6 @@ func (s *EonPubKeySyncer) Start(ctx context.Context, runner service.Runner) erro
 		Context: ctx,
 	}
 	s.keyBroadcastCh = make(chan *bindings.KeyBroadcastContractEonKeyBroadcast, channelSize)
-	runner.Defer(func() {
-		close(s.keyBroadcastCh)
-	})
 	subs, err := s.KeyBroadcast.WatchEonKeyBroadcast(watchOpts, s.keyBroadcastCh)
 	// FIXME: what to do on subs.Error()
 	if err != nil {

rolling-shutter/medley/chainsync/syncer/keyperset.go

@@ -66,9 +66,6 @@ func (s *KeyperSetSyncer) Start(ctx context.Context, runner service.Runner) erro
 		}
 	}
 	s.keyperAddedCh = make(chan *bindings.KeyperSetManagerKeyperSetAdded, channelSize)
-	runner.Defer(func() {
-		close(s.keyperAddedCh)
-	})
 	subs, err := s.Contract.WatchKeyperSetAdded(watchOpts, s.keyperAddedCh)
 	// FIXME: what to do on subs.Error()
 	if err != nil {

rolling-shutter/medley/chainsync/syncer/shutterstate.go

@@ -55,9 +55,6 @@ func (s *ShutterStateSyncer) Start(ctx context.Context, runner service.Runner) e
 		return err
 	}
 	runner.Defer(subs.Unsubscribe)
-	runner.Defer(func() {
-		close(s.pausedCh)
-	})
 
 	s.unpausedCh = make(chan *bindings.KeyperSetManagerUnpaused)
 	subs, err = s.Contract.WatchUnpaused(watchOpts, s.unpausedCh)
@@ -66,9 +63,6 @@ func (s *ShutterStateSyncer) Start(ctx context.Context, runner service.Runner) e
 		return err
 	}
 	runner.Defer(subs.Unsubscribe)
-	runner.Defer(func() {
-		close(s.unpausedCh)
-	})
 
 	runner.Go(func() error {
 		return s.watchPaused(ctx)

rolling-shutter/medley/chainsync/syncer/unsafehead.go

@@ -33,9 +33,6 @@ func (s *UnsafeHeadSyncer) Start(ctx context.Context, runner service.Runner) err
 		return err
 	}
 	runner.Defer(subs.Unsubscribe)
-	runner.Defer(func() {
-		close(s.newLatestHeadCh)
-	})
 	runner.Go(func() error {
 		return s.watchLatestUnsafeHead(ctx)
 	})