feat: use persistent configuration file

pkg/selfsigned/cert.go

@@ -19,15 +19,24 @@ import (
 	"github.com/pkg/errors"
 )
 
-func NewLANCert() (*tls.Certificate, error) {
+func NewLANKeyPair() ([]byte, []byte, error) {
 	hosts, err := network.GetLANIPv4Addrs()
 	if err != nil {
-		return nil, errors.WithStack(err)
+		return nil, nil, errors.WithStack(err)
 	}
 
 	hosts = append(hosts, "127.0.0.1")
 
 	rawCert, rawKey, err := NewCertKeyPair(hosts...)
+	if err != nil {
+		return nil, nil, errors.WithStack(err)
+	}
+
+	return rawCert, rawKey, nil
+}
+
+func NewLANCert() (*tls.Certificate, error) {
+	rawCert, rawKey, err := NewLANKeyPair()
 	if err != nil {
 		return nil, errors.WithStack(err)
 	}