filter: Make the code mor idiomatic and drop the context dependency

There is no need to await ctx.Done() in the filter loop as we can
simply stop looping when the input channel is closed. We'll also close
our output channel now and make this code more consistent.

broadcast.go

@@ -18,7 +18,7 @@ type broadcast struct {
 func newBroadcast(ctx context.Context, src <-chan ServerList) *broadcast {
 	b := &broadcast{
 		ctx:  ctx,
-		src:  newServerListFilter(ctx, src),
+		src:  filterEqualServerList(src),
 		tgts: make(map[Listener]bool),
 		add:  make(chan Listener),
 		rem:  make(chan Listener),

filter.go

@@ -1,30 +1,17 @@
 package main
 
-import "context"
-
-func newServerListFilter(ctx context.Context, in <-chan ServerList) <-chan ServerList {
+func filterEqualServerList(in <-chan ServerList) <-chan ServerList {
 	out := make(chan ServerList)
-	go doFilter(ctx, in, out)
-	return out
-}
 
-func doFilter(ctx context.Context, in <-chan ServerList, out chan ServerList) {
-	var prev ServerList
+	go func() {
+		defer close(out)
+
+		var prev ServerList
 
-looping:
-	for {
-		select {
-		case <-ctx.Done():
-			return
-		case next := <-in:
+		for next := range in {
 			if len(prev) == len(next) {
 				equal := true
 
-				// make a sacrifice for the ssa range check elimination gods
-				n := len(prev)
-				_ = prev[n-1]
-				_ = next[n-1]
-
 				for i := range prev {
 					if !prev[i].Equal(next[i]) {
 						equal = false
@@ -33,12 +20,14 @@ looping:
 				}
 
 				if equal {
-					continue looping
+					continue
 				}
 			}
 
 			prev = next
 			out <- next
 		}
-	}
+	}()
+
+	return out
 }