Lock lowdb file (#95)

* Lock lowdb file when using. Do not allow caching

* Linter fixes

* Move to non-jslib lowdbstorage to allow for lockfile

* update jslib

* Must ensure db file exists prior to initialization

proper-lockfile throws if the file its locking does not exist

* update jslib

* Let base handle file initialization

src/services/lowdbStorage.service.ts

@@ -0,0 +1,29 @@
+import * as fs from 'fs';
+import * as lock from 'proper-lockfile';
+
+import { LogService } from 'jslib/abstractions/log.service';
+
+import { LowdbStorageService as LowdbStorageServiceBase } from 'jslib/services/lowdbStorage.service';
+
+import { Utils } from 'jslib/misc/utils';
+
+export class LowdbStorageService extends LowdbStorageServiceBase {
+    constructor(logService: LogService, defaults?: any, dir?: string, allowCache = false, private requireLock = false) {
+        super(logService, defaults, dir, allowCache);
+    }
+
+    protected async lockDbFile<T>(action: () => T): Promise<T> {
+        if (this.requireLock && !Utils.isNullOrWhitespace(this.dataFilePath)) {
+            this.logService.info('acquiring db file lock');
+            return await lock.lock(this.dataFilePath, { retries: 3 }).then(release => {
+                try {
+                    return action();
+                } finally {
+                    release();
+                }
+            });
+        } else {
+            return action();
+        }
+    }
+}