lib/model, lib/nat: More service termination speedup (#5884)

lib/model/folder.go

@@ -423,6 +423,12 @@ func (f *folder) scanSubdirs(subDirs []string) error {
 		var iterError error
 
 		f.fset.WithPrefixedHaveTruncated(protocol.LocalDeviceID, sub, func(fi db.FileIntf) bool {
+			select {
+			case <-f.ctx.Done():
+				return false
+			default:
+			}
+
 			file := fi.(db.FileInfoTruncated)
 
 			if err := batch.flushIfFull(); err != nil {
@@ -507,6 +513,12 @@ func (f *folder) scanSubdirs(subDirs []string) error {
 			return true
 		})
 
+		select {
+		case <-f.ctx.Done():
+			return f.ctx.Err()
+		default:
+		}
+
 		if iterError == nil && len(toIgnore) > 0 {
 			for _, file := range toIgnore {
 				l.Debugln("marking file as ignored", f)