ServeDir and SPAIndex conflict: NotFound ignored due to fasthttp.FS

[aleksei0807]

Expected Behavior

ServeDir() serves files from directory and when gets 404 it should call NotFound() instead of bare fasthttp processing

Current Behavior

ServeDir() ignores NotFound() due to fasthttp.FS usage

Possible Solution

Embed fasthttp.FS, fix NotFound() processing, replace it in ServeDir etc.

Steps to Reproduce (for bugs)

See first 3s version

Context

Serving files in SPA

Your Environment

• Version used: 1.1.0-rc15
• Environment name and version (e.g. Go1.9 on CentOS 7, kernel 4.11.2): go version go1.10.2 darwin/amd64; Darwin Kernel Version 17.5.0: Fri Apr 13 19:32:32 PDT 2018; root:xnu-4570.51.2~1/RELEASE_X86_64 x86_64
• Server type and version: -
• Operating System and version: MacOS 10.13.4
• Link to your project: https://github.com/gramework/3s

[kirillDanshin]

@toby3d no, that's another issue