Function command 

pub fn command<I, O, E>(
    config: Config,
    function: CommandFn<I, O, E>,
) -> Result<Command<I, O, E>, CriusError>
where
    E: From<CriusError>,

Use this function to construct a circuit breaker without a fallback function.

Example:

// Define a simple circuit breaker command:
let mut cmd = command(Config::default(), |n| {
    if n > 10 {
        Err(ExampleError)
    } else {
        Ok(n * 2)
    }}).unwrap();

// and run it with an example input:
let result = cmd.run(10);
assert_eq!(Ok(20), result)