Jester says expects a GC-safe OnRequest closure on latest devel with or without --threads:on
```nim
../../c/Users/lxdong/.nimble/pkgs/jester-0.4.1/jester.nim(473, 8) Error: type mismatch: got <proc (req: Request): Future[system.void]{.closure, locks: <unknown>.}, Settings>
but expected one of:
proc run(onRequest: OnRequest; settings: Settings)
  first type mismatch at position: 1
  required type: OnRequest
  but expression 'proc (req: httpbeast.Request): Future[void] = result = handleRequest(jes, req)' is of type: proc (req:
Request): Future[system.void]{.closure, locks: <unknown>.}
  This expression is not GC-safe. Annotate the proc with {.gcsafe.} to get extended error information.
proc run(onRequest: OnRequest)
  first type mismatch at position: 1
  required type: OnRequest
  but expression 'proc (req: httpbeast.Request): Future[void] = result = handleRequest(jes, req)' is of type: proc (req:
Request): Future[system.void]{.closure, locks: <unknown>.}
  This expression is not GC-safe. Annotate the proc with {.gcsafe.} to get extended error information.

expression: run(proc (req: httpbeast.Request): Future[void] = result = handleRequest(jes, req),
    initSettings(self.settings.port, self.settings.bindAddr))