Imports of fileserver command

PathSynopsis
expvarPackage expvar provides a standardized interface to public variables, such as operation counters in servers.
flagPackage flag implements command-line flag parsing.
github.com/valyala/fasthttpPackage fasthttp provides fast HTTP server and client API.
github.com/valyala/fasthttp/expvarhandlerPackage expvarhandler provides fasthttp-compatible request handler serving expvars.
logPackage log implements a simple logging package.