extern crate serde_json; // 1.0.38
use serde_json::Value;

fn sort_json(s: &str) -> String {
    let obj: Value = serde_json::from_str(s).expect("Unable to deserialize JSON object");
    serde_json::to_string(&obj).expect("Unable to serialize JSON object")
}

fn main() {
    println!("{:?}", sort_json(r#"{"c": 3, "b": 2, "a": 1, "nested": {"z": 1, "a": 2}}"#));
}