let mut interval = match args.next() {
            Some(arg) => {
                let i: String = arg.parse().unwrap();
                match i {
                    "s" | "sec" | "seconds" => {interval = "seconds";},
                    "m" | "min" | "minutes" => {interval = "minutes"}
                    _ => return Err("Unsupported interval amount"),
                }
            },
            None => return Err("Didn't get an interval amount"),
        };

//two problems: interval not in scope in the match arm
//mismatched types between "s": expected struct `std::string::String`, found reference