Golangcilint in build pipeline and fix lint errors

- Fix bad permissions bits for files
- VPNSP is 'private internet access' instead of 'pia' (retro compatible)
- Check errors of deferred unsetEnv functions in params package
-  Other lint errors fixing and code simplifications

internal/settings/firewall.go

@@ -1,34 +1,34 @@
-package settings
-
-import (
-	"net"
-	"strings"
-
-	"github.com/qdm12/private-internet-access-docker/internal/params"
-)
-
-// Firewall contains settings to customize the firewall operation
-type Firewall struct {
-	AllowedSubnets []net.IPNet
-}
-
-func (f *Firewall) String() string {
-	var allowedSubnets []string
-	for _, net := range f.AllowedSubnets {
-		allowedSubnets = append(allowedSubnets, net.String())
-	}
-	settingsList := []string{
-		"Firewall settings:",
-		"Allowed subnets: " + strings.Join(allowedSubnets, ", "),
-	}
-	return strings.Join(settingsList, "\n |--")
-}
-
-// GetFirewallSettings obtains firewall settings from environment variables using the params package.
-func GetFirewallSettings(params params.ParamsReader) (settings Firewall, err error) {
-	settings.AllowedSubnets, err = params.GetExtraSubnets()
-	if err != nil {
-		return settings, err
-	}
-	return settings, nil
-}
+package settings
+
+import (
+	"net"
+	"strings"
+
+	"github.com/qdm12/private-internet-access-docker/internal/params"
+)
+
+// Firewall contains settings to customize the firewall operation
+type Firewall struct {
+	AllowedSubnets []net.IPNet
+}
+
+func (f *Firewall) String() string {
+	allowedSubnets := make([]string, len(f.AllowedSubnets))
+	for i := range f.AllowedSubnets {
+		allowedSubnets[i] = f.AllowedSubnets[i].String()
+	}
+	settingsList := []string{
+		"Firewall settings:",
+		"Allowed subnets: " + strings.Join(allowedSubnets, ", "),
+	}
+	return strings.Join(settingsList, "\n |--")
+}
+
+// GetFirewallSettings obtains firewall settings from environment variables using the params package.
+func GetFirewallSettings(paramsReader params.Reader) (settings Firewall, err error) {
+	settings.AllowedSubnets, err = paramsReader.GetExtraSubnets()
+	if err != nil {
+		return settings, err
+	}
+	return settings, nil
+}