Create close channel first inside initialize method

[scirlig-ellation]

Background

When we start the worker by calling the Start method, the application may fail due to AWS access rights or any AWS error, in that case we retry calling start couple of times. If retrying a certain amount of times is unsuccessful we handle the error and exit our program.

However we also have a signal listener which shuts down the application gracefully, and also calls Shutdown method. Considering our workers always failed to start due to failed initialize
When the Shutdown method inside the library is called, it attempts to close stop channel which was not yet created:

worker.go#L134

close(*w.stop)

Solution

I suggest to create the stop channel & and waitGroup in the first place when calling initialize method to avoid panics when calling the Shutdown method

Here's a small example of how our Start looks like:

Start

var retries int
err := w.Start()
for err != nil && retries < app.config.Workers.MaxRetries {
	app.logger.Error(err)
	time.Sleep(5 * time.Second)
	err = w.Start()
	retries++
}
errChan <- err

[taoj-action]

We can do this by adding nil check at:
https://github.com/vmware/vmware-go-kcl/blob/master/clientlibrary/worker/worker.go#L139

	if w.done || w.stop == nil {
		return
	}