Merge Strings Alternately in Rust

merge_alternately.rs

use itertools::Itertools;

fn main() {
    assert_eq!(
        "a1b2c3def",
        merge_alternately_itertools("abcdef".to_string(), "123".to_string())
    );
    assert_eq!(
        "a1b2c3456",
        merge_alternately_itertools("abc".to_string(), "123456".to_string())
    );
}

// I know I can simplify code below but I insist this.
pub fn merge_alternately_itertools(word1: String, word2: String) -> String {
    let mut ans = String::new();

    ans = word1.chars().interleave(word2.chars()).collect();

    ans
}