Suave 2.x NLog adapter

let logger = 
    let convertLevel = function
        | Logging.LogLevel.Debug -> LogLevel.Debug
        | Logging.LogLevel.Verbose -> LogLevel.Trace
        | Logging.LogLevel.Info -> LogLevel.Info
        | Logging.LogLevel.Warn -> LogLevel.Warn
        | Logging.LogLevel.Error -> LogLevel.Error
        | Logging.LogLevel.Fatal -> LogLevel.Fatal
    let name = "WebService" 

    let log = LogManager.GetLogger(name)
    let culture = Globalization.CultureInfo.InvariantCulture
    { new Logging.Logger with
        member __.name = [|name|]
        member __.log(level: Logging.LogLevel) f = 
            async {
                let lvl = convertLevel level
                if log.IsEnabled lvl then
                    let m = f level
                    let message = sprintf "%A" m.value
                    let name = String.Join(".", m.name)
                    match m.fields |> Map.tryFind "errors" with
                    | None ->  log.Log(LogEventInfo(lvl, name, culture, message, null))
                    | Some ex -> log.Log(LogEventInfo(lvl, name, culture, message, null, unbox ex)) }

        member this.logWithAck level f = (this :> Logging.Logger).log level f }