Run a query against PostgreSQL with F# using the Npgsql driver

Using_postgres_from_FSharp_with_driver.fs

async {
    use conn = new NpgsqlConnection (connectionString)
    use cmd = conn.CreateCommand (CommandText="SELECT field1, field5 FROM some_table WHERE foo=:bar")
    cmd.Parameters.AddWithValue ("bar", "baz) |> ignore
    do! conn.OpenAsync () |> Async.AwaitTask // Automatically closed when disposed
    use! reader = cmd.ExecuteReaderAsync() |> Async.AwaitTask
    // Need a function to iterate through results
    let rec readData results = async {
        let! hasRecord = reader.ReadAsync () |> Async.AwaitTask
        match hasRecord with
        | true ->
            let field1 = reader.GetString 0 // 0-based index of selected fields
            let field5 = reader.GetString 1
            return! readData ((field1, field5) :: results)
        | false -> return results |> List.rev // end of reader, so reverse list and return
    }
    // Now pass an empty list to that function
    return! List.empty |> readData
}