简单事件模拟器

event.go

type eventGenerator struct {
      eventCh chan int
      ctx context.Context
      cancel context.CancelFunc
  }

  func NewEventGenerator(ctx context.Context) *eventGenerator {
      // better to get context from others place, even this is a most up level controller
      // because you can use `context.Background()` as argument if this is the most up level one
      ctx, cancel := context.WithCancel(ctx)
      return &eventGenerator{
          // don't forget to `make` a channel,
          // if you skip it, Go won't give you any warning
          // And anything you try to send to it would be ignored!
          // No Warning!
          eventCh: make(chan int),
          ctx: ctx,
          cancel: cancel,
      }
  }

  func (e *eventGenerator) Start() {
      go func() {
          defer close(e.eventCh)
          for {
              select {
              case _, closed := <- e.ctx.Done():
                  if closed {
                      return
                  }
              default:
                  e.eventCh <- 1
              }
          }
      }()
  }
  func (e *eventGenerator) Events() <-chan int { return e.eventCh }
  func (e *eventGenerator) Close() { e.cancel() }