package concurrent
  
  import "context"
  
  // Executor replace go keyword to start a new goroutine
  // the goroutine should cancel itself if the context passed in has been cancelled
  // the goroutine started by the executor, is owned by the executor
  // we can cancel all executors owned by the executor just by stop the executor itself
  // however Executor interface does not Stop method, the one starting and owning executor
  // should use the concrete type of executor, instead of this interface.
  type Executor interface {
  	// Go starts a new goroutine controlled by the context
  	Go(handler func(ctx context.Context))
  }