[BUG] prest crashes if user set a cache directory that does not exists in filesystem

[moinologics]

steps to reproduce

• pull the latest docker image
• enable cache & set some cache directory (which not exists in filesystem, for example /some/non-existing/path) in prest.toml
• start the server
• hit the http endpoint (first time it will show error)

you will see like this in response

PANIC: runtime error: invalid memory address or nil pointer dereference
goroutine 33 [running]:
github.com/urfave/negroni/v3.(*Recovery).ServeHTTP.func1()
	/home/runner/go/pkg/mod/github.com/urfave/negroni/v3@v3.0.0/recovery.go:168 +0x140
panic({0x51c020, 0x9c3c10})
	/opt/hostedtoolcache/go/1.20.8/x64/src/runtime/panic.go:884 +0x1f4
github.com/tidwall/buntdb.(*Tx).lock(0x400022a440?)
	/home/runner/go/pkg/mod/github.com/tidwall/buntdb@v1.3.0/buntdb.go:1140 +0x24

when you hit url second time, it will not crash but will create cache files in /app instead of creating cache path setted by user in prest.toml file

[arxdsilva]

@moinologics I've raised a PR for a potential solution, but could you also provide the full stack trace of the panic error?

Thanks

[arxdsilva]

released in https://github.com/prest/prest/releases/tag/v1.4.2