[FEATURE REQUEST] Handler function middleware

[rugwirobaker]

Is your feature request related to a problem? Please describe.
Do plan to support middleware functions that behave the same way for example gorilla mux.Middware do? If not how do logging??

[hibiken]

@rugwirobaker Thanks for this feature request!

Could you provide an example code for a potential API for middleware support?

Alternatively, can you simply write a middleware function and wrap your handlers with that middleware?

func loggingMiddleware(h asynq.Handler) asynq.Handler {
    return asynq.HandlerFunc(func(ctx context.Context, t *asynq.Task) error {
        // log something before handler processes the task
        h.ProcessTask(ctx, t)
        // log something after handler processed the task
    })
}

mux := asynq.ServeMux()
mux.HandleFunc("something", loggingMiddleware(myHandler))

would that work? Or should the package offer better support for middleware chain?

[rugwirobaker]

For most use cases this works fine but in cases where you have a lot of middleware functions having something like:
mux.Use(someMiddlware) or mux.Add(someMiddleware) it would help avoid the clutter.

[hibiken]

Ok that makes sense.
Let's add Use method to add middlewares to the chain, similar to gorilla/mux#Route.Use. The method should be a variadic function that takes any number of middleware functions. They should be executed in the order that they are applied.

Example:

mux := asynq.ServeMux()
mux.Use(loggingMiddleware)
mux.HandleFunc("something", myHandler)