Rust hashmap example usage code

hashmapexample.rs

// hashmap example - for reference
let mut sample: HashMap<String, i32> = HashMap::new();

sample.insert("one".to_string(), 1);
sample.insert("two".to_string(), 2);
sample.insert("three".to_string(), 3);
sample.insert("four".to_string(), 4);
for (key, value) in sample.iter() {
    println!("{} - {}", key, value);
}
println!("four: {:?}", sample.get("four").unwrap());