feat(daemon): add checkLockFile helper

config/daemon/check-lock-file.js

@@ -0,0 +1,19 @@
+// @flow
+import fs from 'fs';
+import path from 'path';
+import { promisify } from 'util';
+import eres from 'eres';
+
+import { getZcashFolder } from './get-zcash-folder';
+
+const ZCASH_LOCK_FILE = '.lock';
+
+export const checkLockFile = async (zcashPath?: string) => {
+  try {
+    const myPath = zcashPath || getZcashFolder();
+    const [cannotAccess] = await eres(promisify(fs.access)(path.join(myPath, ZCASH_LOCK_FILE)));
+    return !cannotAccess;
+  } catch (err) {
+    return false;
+  }
+};