Listen on custom address (#140)

Co-Authored-By: eternal-flame-AD <ef@eternalflame.info>

config/config.go

@@ -10,10 +10,12 @@ import (
 // Configuration is stuff that can be configured externally per env variables or config file (config.yml).
 type Configuration struct {
 	Server struct {
-		Port int `default:"80"`
-		SSL  struct {
+		ListenAddr string `default:""`
+		Port       int    `default:"80"`
+		SSL        struct {
 			Enabled         *bool  `default:"false"`
 			RedirectToHTTPS *bool  `default:"true"`
+			ListenAddr      string `default:""`
 			Port            int    `default:"443"`
 			CertFile        string `default:""`
 			CertKey         string `default:""`