Logging example after applying the writer monad

post-writer.fs

let o x = x :> obj

let getSuperUserData super =
  writer {
    let sw = Stopwatch.StartNew()
    let service = getService ()
    let result = service.getSuperUserDetails super
    do! write ("serviceElapsed", o sw.ElapsedMilliseconds)

    match result with
    | Ok res ->
      do! write ("serviceResult", o "success")
      return (Some res)

    | Error e ->
      do! write ("serviceResult", o "error")
      do! write ("error", o e)
      return None
  }

let doWork input =
  writer {
    let sw = Stopwatch.StartNew()
    do! write ("userId", o input.UserId)

    do!
      match input.Status with
      | Valid -> write ("status", o "valid")
      // ...

      | Invalid -> write ("status", o "invalid")
      // ...

    let! result =
      match input.Subscription with
      | Basic -> retn None
      | Super super -> getSuperUserData (super, log)

    do! write ("totalElapsed", o sw.ElapsedMilliseconds)
    // ...

    return result
  }

open System.Text.Json

[<EntryPoint>]
let main input =
  let writer = doWork input
  let (_, logs) = run writer

  Map.ofList logs
  |> JsonSerializer.Serialize
  |> printfn "%s"

  0