Apply suggestion

Co-authored-by: Aaron Andersen <aaron@fosslib.net>

nixos/modules/services/mail/goeland.nix

@@ -40,13 +40,17 @@ in
     services.goeland.settings.database = "${cfg.stateDir}/goeland.db";
 
     systemd.services.goeland = {
-      serviceConfig = let confFile = tomlFormat.generate "config.toml" cfg.settings; in {
-        ExecStart = "${pkgs.goeland}/bin/goeland run -c ${confFile}";
-        User = "goeland";
-        Group = "goeland";
-        StateDirectory = "goeland";
-        StateDirectoryMode = "0750";
-      };
+      serviceConfig = let confFile = tomlFormat.generate "config.toml" cfg.settings; in mkMerge [
+        {
+          ExecStart = "${pkgs.goeland}/bin/goeland run -c ${confFile}";
+          User = "goeland";
+          Group = "goeland";
+        }
+        (mkIf (cfg.stateDir == "/var/lib/goeland") {
+          StateDirectory = "goeland";
+          StateDirectoryMode = "0750";
+        })
+      ];
       startAt = cfg.schedule;
     };