use range over integers where possible

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

container/container.go

@@ -349,7 +349,7 @@ func (x *Container) SetAttribute(key, value string) {
 	attrs := x.v2.GetAttributes()
 	ln := len(attrs)
 
-	for i := 0; i < ln; i++ {
+	for i := range ln {
 		if attrs[i].GetKey() == key {
 			attrs[i].SetValue(value)
 			return

eacl/target.go

@@ -150,7 +150,7 @@ func SetTargetECDSAKeys(t *Target, pubs ...*ecdsa.PublicKey) {
 		binKeys = make([][]byte, 0, ln)
 	}
 
-	for i := 0; i < ln; i++ {
+	for i := range ln {
 		binKeys = append(binKeys, (*keys.PublicKey)(pubs[i]).Bytes())
 	}
 
@@ -163,7 +163,7 @@ func SetTargetAccounts(t *Target, accs ...util.Uint160) {
 	account := make([]user.ID, len(accs))
 	ln := len(accs)
 
-	for i := 0; i < ln; i++ {
+	for i := range ln {
 		account[i] = user.NewFromScriptHash(accs[i])
 	}
 
@@ -180,7 +180,7 @@ func TargetECDSAKeys(t *Target) []*ecdsa.PublicKey {
 
 	pubs := make([]*ecdsa.PublicKey, ln)
 
-	for i := 0; i < ln; i++ {
+	for i := range ln {
 		p := new(keys.PublicKey)
 		if p.DecodeBytes(binKeys[i]) == nil {
 			pubs[i] = (*ecdsa.PublicKey)(p)

stat/pool.go

@@ -39,7 +39,7 @@ func (s *PoolStat) OperationCallback(nodeKey []byte, endpoint string, method Met
 	mon, ok := s.monitors[k]
 	if !ok {
 		methods := make([]*methodStatus, MethodLast)
-		for i := MethodBalanceGet; i < MethodLast; i++ {
+		for i := range MethodLast {
 			methods[i] = &methodStatus{name: i.String()}
 		}