Rust: updating an array field of mutable struct in a seperate function

main.rs

use std::env;
use std::fs::File;
use serde::{Deserialize, Serialize};

#[derive(Serialize, Deserialize, Debug)]
struct Site {
    id: String,
    #[serde(skip_serializing_if = "Option::is_none")]
    status_changed: Option<bool>,
    #[serde(skip_serializing_if = "Option::is_none")]
    text: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    value: Option<f32>
}

#[derive(Serialize, Deserialize, Debug)]
struct Plan {
    sites: Vec<Site>
}

fn main() {

    let mut args = env::args();
    args.next();

    let path = args.next()
        .expect("no argument");
    let file = File::open(&path)
        .expect("can't read file");
    let mut plan: Plan = serde_json::from_reader(&file)
        .expect("can't read to json");

    // plan.sites = plan.sites.into_iter()
    //     .map(|mut s| {
    //         s.status_changed = Option::from(true);
    //         s
    //     })
    //     .collect();
    //
    // plan.sites.iter().for_each(|s| {
    //     println!("{}, {:?}", s.id, s.status_changed)
    // });

    run(&mut plan);

    let file = File::create(&path)
        .expect("can't create file");
    serde_json::to_writer_pretty(&file, &plan)
        .expect("can't write to json file");
}

fn run (plan: &mut Plan) {
    for site in plan.sites.iter_mut() {
        let id = &site.id;
        println!("{}", id);
        site.status_changed = Option::from(true)
    }
}