feat(*): Support for handling panic error

[linhbkhn95]

Why did we need it?

• Allow users can handle the panic error if they want
  Example:

func main() {

	srv := asynq.NewServer(
		asynq.RedisClientOpt{
			Addr: redisAddr,
		},
		asynq.Config{
			// Specify how many concurrent workers to use
			Concurrency: 10,
			// Optionally specify multiple queues with different priority.
			Queues: map[string]int{
				"critical": 6,
				"default":  3,
				"low":      1,
			},
			ErrorHandler: asynq.ErrorHandlerFunc(HandleErrorFunc),
		},
	)

	// mux maps a type to a handler
	mux := asynq.NewServeMux()
	mux.HandleFunc(tasks.TypeEmailDelivery, tasks.HandleEmailDeliveryTask)
	mux.Handle(tasks.TypeImageResize, tasks.NewImageProcessor())
	// ...register other handlers...

	if err := srv.Run(mux); err != nil {
		log.Fatalf("could not run server: %v", err)
	}
}

// The ErrorHandlerFunc type is an adapter to allow the use of  ordinary functions as a ErrorHandler.
// If f is a function with the appropriate signature, ErrorHandlerFunc(f) is a ErrorHandler that calls f.
// HandleError calls fn(ctx, task, err)
func HandleErrorFunc(ctx context.Context, task *asynq.Task, err error) {
	if asynq.IsPanicError(err) {
		// Handle panic error here.
	}
}

fixed #487

[codecov]

Codecov Report

Merging #491 (f915368) into master (cbb1be3) will increase coverage by 0.03%.
The diff coverage is 87.50%.

@@            Coverage Diff             @@
##           master     #491      +/-   ##
==========================================
+ Coverage   68.34%   68.37%   +0.03%     
==========================================
  Files          27       27              
  Lines        3829     3836       +7     
==========================================
+ Hits         2617     2623       +6     
- Misses        928      929       +1     
  Partials      284      284              

Impacted Files	Coverage Δ
server.go	85.47% <ø> (ø)
internal/errors/errors.go	61.44% <66.66%> (+0.19%)	⬆️
processor.go	79.23% <100.00%> (+0.35%)	⬆️

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[imcvampire]

LGTM! Please review and merge it!

[hibiken]

@linhbkhn95 Thank you for opening a PR, and sorry for the delay in response.
I'd like to avoid adding yet another callback in the Config.
I think a better solution is to wrap in a custom error so that users can leverage the ErrorHandler to handle panic.

Please discuss the API in the #487.

[linhbkhn95]

@hibiken tks for your suggestion. I updated it.

[linhbkhn95]

@hibiken Please review it help me

[kamikazechaser]

+1 This would be a useful feature.

[ping-localhost]

This would be very useful to check if a panic happened or just a "boring" error. Hope this will get merged at some point.

[kamikazechaser]

LGTM, I have been using this feature for a few weeks now.

Maybe github.com/test-go/testify is an unnecessary dependency because asynq already uses github.com/google/go-cmp in other tests so there will be some little inconsistency.

[kamikazechaser]

@hibiken We can merge this.

[linhbkhn95]

@hibiken I don't know whether u have a concern about this PR?
I really wanna use this feature this root repo instead of my repo

[kamikazechaser]

Thanks @linhbkhn95! It will be included in the next release tag.

[hibiken]

@kamikazechaser Please discuss API changes with me before merging these PRs.