add pause command

lib/tasks/pause.js

@@ -0,0 +1,26 @@
+const Task = require('./task');
+const {TaskName} = require('../utils/constants');
+
+class TaskPause extends Task {
+  constructor(logger, opts, parentTask) {
+    super(logger, opts);
+
+    this.length = this.data.length;
+  }
+
+  get name() { return TaskName.Pause; }
+
+  async exec(cs, ep) {
+    super.exec(cs);
+    this.timer = setTimeout(this.notifyTaskDone.bind(this), this.length * 1000);
+    await this.awaitTaskDone();
+  }
+
+  async kill() {
+    super.kill();
+    clearTimeout(this.timer);
+    this.notifyTaskDone();
+  }
+}
+
+module.exports = TaskPause;