Start runs all tasks and monitors channel events.

添加一个新的订阅者，订阅全部主题

Task implements the Worker interface.

A deadlock happens when a group of goroutines are waiting for each other and none of them is able to proceed. The program will get stuck on the channe

想弄清楚slice遍历时被修改到底会发生什么. 结果是安全失败. 并不意味着是线程安全的.

Pipeline source->filter->print

STARTUPDATES OMIT

STOPNAIVEMERGECLOSE OMIT

The deferred func above will only run when the func ends not when the deferred func’s surrounding block ends (the area inside curly braces containing

createConnection is a factory method that will be called by the pool when a new connection is needed.

dedupeLoop extends mergedLoop with deduping of fetched items.

Do not use defer inside a loop unless you are sure about what you are doing. It may not work as expected. However, in some situations it will be handy

So, when a method with a value-receiver is used with defer, the receiver will be copied (in this case Car) at the time of registering and the changes

TODO: in a longer talk: move the Subscribe function onto a Reader type, to support dynamically adding and removing Subscriptions. Reader should dedup

init is called when the system is inited.

STOPCLOSE OMIT loopCloseOnly is a version of loop that includes only the logic that handles Close.

loopFetchOnly is a version of loop that includes only the logic that calls Fetch.

loopSendOnly is a version of loop that includes only the logic for sending items to s.updates.

* There's no formal definition of a pipeline in Go; it's just one of many kinds of concurrent programs. Informally, a pipeline is a series of stages c

**在发布订阅模型中，每条消息都会传送给多个订阅者。发布者通常不会知道、也不关心哪一 个订阅者正在接收主题消息。订阅者和发布者可以在运行时动态添加是一种松散的耦合关 心，这使得系统的复杂性可以随时间的推移而增长。在现实生活中，不同城市的象天气预报 之类的应用就可以应用这个并发模式。 */

For example: we must a execute some command so before that we must to create new terminal session and provide our user name and command