Run modernize to rewrite some older go constructs to newer ones

Mostly using slice.Sort, using min/max, slices.Concat, range of int and
fmt.Appendf for byte slices instead of strings.

queue/hook_test.go

@@ -429,7 +429,7 @@ func TestFromIDIncomingDelivery(t *testing.T) {
 	tcheck(t, err, "get added hook")
 	h.URL = hs.URL
 	handler = handleError
-	for i := 0; i < len(hookIntervals); i++ {
+	for i := range hookIntervals {
 		hookDeliver(pkglog, h)
 		<-hookDeliveryResults
 		err := DB.Get(ctxbg, &h)
@@ -557,7 +557,7 @@ func TestHookListFilterSort(t *testing.T) {
 	// Descending by submitted,id.
 	l, err = HookList(ctxbg, HookFilter{}, HookSort{Field: "Submitted"})
 	tcheck(t, err, "list")
-	ll := append(append([]Hook{}, hlrev[1:]...), hl[5])
+	ll := append(slices.Clone(hlrev[1:]), hl[5])
 	tcompare(t, l, ll)
 
 	// Filter by all fields to get a single.

queue/queue.go

@@ -1372,7 +1372,7 @@ func deliver(log mlog.Log, resolver dns.Resolver, m0 Msg) {
 		}
 
 		backoff = time.Duration(7*60+30+jitter.IntN(10)-5) * time.Second
-		for i := 0; i < m0.Attempts; i++ {
+		for range m0.Attempts {
 			backoff *= time.Duration(2)
 		}
 		m0.Attempts++

queue/queue_test.go

@@ -310,10 +310,10 @@ func TestQueue(t *testing.T) {
 			writeline("250-" + ext)
 		}
 		writeline("250 pipelining")
-		for tx := 0; tx < ntx; tx++ {
+		for range ntx {
 			readline("mail")
 			writeline("250 ok")
-			for i := 0; i < rcpts; i++ {
+			for i := range rcpts {
 				readline("rcpt")
 				if onercpt && i > 0 {
 					writeline("552 ok")
@@ -462,7 +462,7 @@ func TestQueue(t *testing.T) {
 		fmt.Fprintf(server, "235 2.7.0 auth ok\r\n")
 		br.ReadString('\n') // Should be MAIL FROM.
 		fmt.Fprintf(server, "250 ok\r\n")
-		for i := 0; i < nrcpt; i++ {
+		for range nrcpt {
 			br.ReadString('\n') // Should be RCPT TO.
 			fmt.Fprintf(server, "250 ok\r\n")
 		}
@@ -520,7 +520,7 @@ func TestQueue(t *testing.T) {
 
 		// Wait for all results.
 		timer.Reset(time.Second)
-		for i := 0; i < nresults; i++ {
+		for range nresults {
 			select {
 			case <-deliveryResults:
 			case <-timer.C:
@@ -1331,7 +1331,7 @@ func TestListFilterSort(t *testing.T) {
 	// Descending by queued,id.
 	l, err = List(ctxbg, Filter{}, Sort{Field: "Queued"})
 	tcheck(t, err, "list messages")
-	ql := append(append([]Msg{}, qmlrev[1:]...), qml[5])
+	ql := append(slices.Clone(qmlrev[1:]), qml[5])
 	tcompare(t, l, ql)
 
 	// Filter by all fields to get a single.