Upgrade: use context to track or control all the flow

[leijiru1994]

hi，when i use this repo, i found that no way to track or control the flow。

so, i think we should use context in store interface like below

• I will push mr and hope can be reviewed in your free time
  

[mojocn]

个人观点：
如果 context 没有被用来传递值 或者 context 没有用来控制 goroutine cancel ，
增加context 参数是没有意义的