useclap::{ArgEnum,Parser};#[derive(Parser)]#[clap(author, version, about, long_about = None)]structCli{/// What mode to run the program in#[clap(arg_enum, value_parser)]mode: Mode,}#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, ArgEnum)]enumMode{Fast,Slow,}fnmain(){letcli=Cli::parse();matchcli.mode{Mode::Fast=>{println!("Hare");}Mode::Slow=>{println!("Tortoise");}}}