use cmd context in cache init functions

[iwpnd]

I just walked through the code and the cache init routine is a bit confusing. The part I'm referencing enhancing with the context is the InitFunc:

tegola/cache/cache.go

Line 136 in 93b917e

type InitFunc func(dict.Dicter) (Interface, error)

This is called by the For method:

tegola/cache/cache.go

Line 165 in 93b917e

func For(cacheType string, config dict.Dicter) (Interface, error) {

Which is invoked by the internal cmd/internal/register/ package:

tegola/cmd/internal/register/caches.go

Line 16 in 93b917e

func Cache(config dict.Dicter) (cache.Interface, error) {

The main value we would get with this plumbing is if tegola is started up and then killed before the cache initializes fully.

I'm not going to block the PR on this request, but just following up on the intent of my comment. Your call if you want to make this change ;-)

Originally posted by @ARolek in #1013 (comment)