lock cache during ROM move operation

main.go

@@ -153,7 +153,9 @@ func moveBuildArtifacts(outDirectory, romDirectory string) bool {
 
 		newROMs = true
 		log.Printf("new build found - moving file %s", v.Name())
+		romCache.Lock() // lock to prevent multiple concurrent goroutines moving the same file
 		err := moveBuildFile(fmt.Sprintf("%s/%s", outDirectory, v.Name()), fmt.Sprintf("%s/%s", romDirectory, v.Name()))
+		romCache.Unlock()
 		if err != nil {
 			log.Printf("failed to move file '%s' from out to rom directory: %v", v.Name(), err)
 			continue
@@ -182,11 +184,16 @@ func isLineageROMZip(v fs.DirEntry) (bool, []string) {
 // http - GET /
 // Writes JSON response for the updater app to know what versions are available to download
 func lineageOSROMListHandler(w http.ResponseWriter, r *http.Request) {
-	romCache.Lock()
-	lineageOSROMs := romCache.ROMs
-	romCache.Unlock()
+	go func() {
+		newBuilds := moveBuildArtifacts("out", "public")
+		if newBuilds {
+			updateROMCache("public")
+		}
+	}()
 
-	httpResponseJSON := &HTTPResponseJSON{Response: lineageOSROMs}
+	romCache.Lock()
+	httpResponseJSON := &HTTPResponseJSON{Response: romCache.ROMs}
+	romCache.Unlock()
 
 	b, err := json.Marshal(httpResponseJSON)
 	if err != nil {
@@ -196,13 +203,6 @@ func lineageOSROMListHandler(w http.ResponseWriter, r *http.Request) {
 	}
 
 	w.Write(b)
-
-	go func() {
-		newBuilds := moveBuildArtifacts("out", "public")
-		if newBuilds {
-			updateROMCache("public")
-		}
-	}()
 }
 
 // Returns a sha256 hash of a file located at the path provided