Reusing provided HTTP context in UnroutedHandler

[bastien-seqone]

Is your feature request related to a problem? Please describe.
We use tusd with our own store to use the SSE-C functionality of the S3 standard and manage encryption. In order to manage our encryption keys, we have middleware that does a lot of business verification and we would like to pass information through the HTTP context.

But in the UnroutedHandler, the handler methods create a new context (ctx.Background()) and do not reuse the HTTP request context provided (r.Context()).

By example,

// PostFile creates a new file upload using the datastore after validating the
// length and parsing the metadata.
func (handler *UnroutedHandler) PostFile(w http.ResponseWriter, r *http.Request) {
	ctx := context.Background() // <- Here
...

Describe the solution you'd like
The Http request context could be used: this would allow middleware to add their own information. I don't believe there is any reason not to use it, but I may have missed something.

Using the same example, it would be :

// PostFile creates a new file upload using the datastore after validating the
// length and parsing the metadata.
func (handler *UnroutedHandler) PostFile(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
...

Describe alternatives you've considered
Using wide available Hashmap, or something like that… but it's not very nice :(

Can you provide help with implementing this feature?
Yep, I think we can manage this little change :)

[Acconut]

Thank you for the detailed report. There were already some attempts to reuse the request context but we encountered some issues which are explained in #361 and #309. I am not sure if these would be resolved by now but I am more than happy to help you try it out! :)

[bastien-seqone]

Sorry I missed the attempts already made.

I've read the solution you propose in the comments in PR #315. I will try to propose something in this way.

[bastien-seqone]

I have just seen that this that this PR #342 seems to be doing the job.

Can you add a test to ensure that the context values from the HTTP request are actually accessible?

It is this missing test that is blocking its approval?

[Acconut]

Yes, this PR is just missing a proper test. However, I would also like to try reusing the request context in such a way that the data storages still work. But that may require some internal refactoring. This would definitely be a better approach instead of such a work around, if you understand what I mean.

[Acconut]

Thanks you for your contribution! In tusd v2, the request context will be accessible in the hooks and stores. Please see #986 for more details and #672 for the development of v2.