Function aoc_driver::get_input_or_file

pub fn get_input_or_file(
    session: &str,
    year: impl Into<i32>,
    day: impl Into<i32>,
    path: impl AsRef<Path>
) -> Result<String>

Gets challenge input - caching at path if required

Checks path to see if input has already been downloaded

If path exists will return the contents

Otherwise download the input for that day and store at path