jwkCache can't be updated concurrently

[dusty-phillips]

Last night my service failed with this traceback:

fatal error: concurrent map writes
goroutine 20214 [running]:
github.com/passageidentity/passage-go.(*App).fetchJWKS(0xc00017a390)
	/opt/render/project/go/pkg/mod/github.com/passageidentity/[email protected]/authentication.go:70 +0xb8
github.com/passageidentity/passage-go.New({0xc00003a33f, 0x18}, 0x0?)
	/opt/render/project/go/pkg/mod/github.com/passageidentity/[email protected]/app.go:41 +0x185
       <snip>

This is because fetchJWKS() is writing to the jwkCache without synchronization: https://github.com/passageidentity/passage-go/blob/main/authentication.go#L70C2-L70C10

I think one of these changes is needed:

• This code needs to be wrapped in a lock or mutex (the reads may need them as well)
• The jwkCache global (defined here) needs to be converted to e.g. sync.Map or similar.
• The cache needs to be stored per-app instead of global
• The documentation needs to be updated to encourage users to create a single app instance (using e.g. OnceValue) instead of one per request.

Great product and service, BTW. Your dev experience blows the competition out of the water.

[dusty-phillips]

This happened again after I tried a singleton app instance, so I think the fourth option doesn’t work.

[bertrmz]

Hi @dusty-phillips, thank you for raising this issue.

We're working on a fix; I'll post an update here when it's available.

[ctran88]

Hi @dusty-phillips very sorry it's been so long!

#88 should address his issue. Once it's merged in and published I will update here with the fixed version.