For getting a Google auth token using Client Login without Google's libraries in F#

ManualGoogleAuth.fs

open System.Text
open System.IO
open System.Net
open System.Web
    let auth = 
        let URL = "https://www.google.com/accounts/ClientLogin"
        let webRequest = HttpWebRequest.Create(URL)
        webRequest.Method <- "POST"
        webRequest.ContentType <- "application/x-www-form-urlencoded"
    
        let postParams = 
            "accountType=" + HttpUtility.UrlEncode(ACCOUNT_TYPE) + // "GOOGLE"
            "&Email=" + HttpUtility.UrlEncode(email) + 
            "&Passwd=" + HttpUtility.UrlEncode(password) + 
            "&source=" + HttpUtility.UrlEncode(SOURCE) + // "COMPANY-APPLICATION-VERSION"
            "&service=" + HttpUtility.UrlEncode(SERVICE) // "analytics"
            

        let postBytes = Encoding.UTF8.GetBytes(postParams)

        webRequest.ContentLength <- (int64)postBytes.Length

        let strmReq = webRequest.GetRequestStream()
        strmReq.Write(postBytes, 0, postBytes.Length)
        strmReq.Close()

        let GetAuthFromResponse (response:WebResponse) =
            let responseStream = response.GetResponseStream()
            let reader = new StreamReader(responseStream)
            let readerResponse = 
                reader.ReadToEnd().Split('\n') 
            let sResponse = 
                readerResponse
                |> Array.filter( fun str -> str.Split('=').Length >= 2 )
                |> Array.map (fun a -> 
                        let subsplit = a.Split('=')
                        (subsplit.[0], subsplit.[1])
                    )
    
            sResponse |> Array.find( fun (key, value) -> key.ToLower() = "auth" ) |> snd   

        let response = webRequest.GetResponse()
        GetAuthFromResponse response