fn main() {
    let features = [
        std::env::var("CARGO_FEATURE_STD2004").is_ok(),
        std::env::var("CARGO_FEATURE_STD2016").is_ok(),
    ];

    let crate_name = std::env::var("CARGO_PKG_NAME")
        .unwrap_or("isotp-rs".into());

    match features.iter()
        .filter(|&&en| en)
        .count() {
        1 => {},
        v => panic!(
            "***`{}`*** at most one of the features `std2004` or `std2016` can be enabled at a time, actual: {}.",
            crate_name,
            v
        )
    }
}