Minimal example resulting in a 410 Gone response

Api.fs

module Api

open Freya.Machines.Http

let root = HttpMachine.Freya <| freyaMachine {
  exists false
  gone true
}

KestrelInterop.fs

/// Provides a nicer interop for configuring and starting the Kestrel server.
module KestrelInterop

open Freya.Core
open Microsoft.AspNetCore.Http
open Microsoft.AspNetCore.Builder
open Microsoft.AspNetCore.Hosting

module ApplicationBuilder =
  let inline useFreya f (app:IApplicationBuilder)=
    let owin : OwinMidFunc = OwinMidFunc.ofFreya f
    app.UseOwin(fun p -> p.Invoke owin)

module WebHost =
  let create () = WebHostBuilder().UseKestrel()
  let bindTo urls (b:IWebHostBuilder) = b.UseUrls urls
  let configure (f : IApplicationBuilder -> IApplicationBuilder) (b:IWebHostBuilder) =
    b.Configure (System.Action<_> (f >> ignore))
  let build (b:IWebHostBuilder) = b.Build()
  let run (wh:IWebHost) = wh.Run()
  let buildAndRun : IWebHostBuilder -> unit = build >> run

Program.fs

module Program

open KestrelInterop

[<EntryPoint>]
let main argv =
  let configureApp =
    ApplicationBuilder.useFreya Api.root

  WebHost.create ()
  |> WebHost.bindTo [|"http://localhost:5000"|]
  |> WebHost.configure configureApp
  |> WebHost.buildAndRun

  0 // return an integer exit code

test.fsproj

<Project Sdk="FSharp.NET.Sdk;Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp1.1</TargetFramework>
    <ServerGarbageCollection>true</ServerGarbageCollection>
    <ConcurrentGarbageCollection>false</ConcurrentGarbageCollection>
  </PropertyGroup>
  <ItemGroup>
    <Compile Include="Api.fs" />
    <Compile Include="KestrelInterop.fs" />
    <Compile Include="Program.fs" />
  </ItemGroup>
  <ItemGroup>
    <PackageReference Include="FSharp.NET.Sdk" Version="1.*" PrivateAssets="All" />
    <PackageReference Include="FSharp.Core" Version="4.*" />
    <PackageReference Include="Freya" Version="4.0.0-alpha-*"/>
    <PackageReference Include="Microsoft.AspNetCore.Server.Kestrel" Version="1.*" />
    <PackageReference Include="Microsoft.AspNetCore.Owin" Version="1.*" />
  </ItemGroup>
</Project>