Function get_optional 

pub fn get_optional<K: AsRef<OsStr>, T: FromStr>(key: K) -> Option<T>

Get the value of the environment variable key as T. If the variable is not set or cannot be parsed, it returns None.

Example

use std::env;
use std::str::FromStr;
use better_config_core::utils::env::get_optional;

let value: Option<u32> = get_optional("MY_ENV_VAR");
match value {
    Some(v) => println!("Value: {}", v),
    None => println!("Variable not set or cannot be parsed"),
}