chore(lint): upgrade linter to v2.4.0

- migrate configuration file
- fix existing code issues
- add exclusion rules
- update linter names

internal/firewall/delete.go

@@ -16,7 +16,7 @@ func isDeleteMatchInstruction(instruction string) bool {
 	fields := strings.Fields(instruction)
 	for i, field := range fields {
 		switch {
-		case field != "-D" && field != "--delete": //nolint:goconst
+		case field != "-D" && field != "--delete":
 			continue
 		case i == len(fields)-1: // malformed: missing chain name
 			return false

internal/firewall/firewall.go

@@ -9,7 +9,7 @@ import (
 	"github.com/qdm12/gluetun/internal/routing"
 )
 
-type Config struct { //nolint:maligned
+type Config struct {
 	runner         CmdRunner
 	logger         Logger
 	iptablesMutex  sync.Mutex

internal/firewall/ip6tables.go

@@ -58,7 +58,7 @@ var ErrPolicyNotValid = errors.New("policy is not valid")
 
 func (c *Config) setIPv6AllPolicies(ctx context.Context, policy string) error {
 	switch policy {
-	case "ACCEPT", "DROP": //nolint:goconst
+	case "ACCEPT", "DROP":
 	default:
 		return fmt.Errorf("%w: %s", ErrPolicyNotValid, policy)
 	}

internal/firewall/iptables.go

@@ -149,7 +149,7 @@ func (c *Config) acceptOutputTrafficToVPN(ctx context.Context,
 ) error {
 	protocol := connection.Protocol
 	if protocol == "tcp-client" {
-		protocol = "tcp" //nolint:goconst
+		protocol = "tcp"
 	}
 	instruction := fmt.Sprintf("%s OUTPUT -d %s -o %s -p %s -m %s --dport %d -j ACCEPT",
 		appendOrDelete(remove), connection.IP, defaultInterface, protocol,