Function load_var 

pub fn load_var<T: FromStr, S: BuildHasher>(
    var_name: &'static str,
    hashmap: Option<&HashMap<String, String, S>>,
) -> Result<T, Error>

Load an environment variable by name and parse it into type T.

This function can also use a hashmap as a fallback or for testing purposes.

Errors

• Environment variable is not present
• Parsing failed