CronSchedule改为必须实现。

Falcon.SugarApi/TimedBackgroundTask/TimedTask.cs

@@ -27,15 +27,16 @@ namespace Falcon.SugarApi.TimedBackgroundTask
         /// <returns>如果继续执行返回True，否则False</returns>
         public abstract Task<bool> Run(CancellationToken cancellationToken);
 
-        /// <summary>
-        /// Timer心跳
-        /// </summary>
-        public virtual int Heartbeat { get; set; } = 1;
 
         /// <summary>
         /// 执行计划的Cron串
         /// </summary>
-        public virtual string CronSchedule { get; set; } = "30 * * * * *";
+        public abstract string CronSchedule { get; }
+
+        /// <summary>
+        /// Timer心跳
+        /// </summary>
+        public virtual int Heartbeat { get; protected set; } = 1;
 
         /// <summary>
         /// 获取下次执行任务的计划