Code shared from the Rust Playground

playground.rs

use serde::Deserialize;
use serde_json;
use std::marker::PhantomData;

#[derive(Deserialize, Debug)]
struct Ping<'a> {
    #[serde(borrow)]
    ping: &'a str,
}

struct Handler<T> {
    data: String,
    _marker: PhantomData<T>,
}

impl<'de, T: Deserialize<'de>> Handler<T> {
    fn new(data: String) -> Self {
        Self {
            data,
            _marker: PhantomData::default(),
        }
    }
    fn handle(&'de self, callback: impl FnOnce(T)) {
        let res: T = serde_json::from_str(&self.data).unwrap();
        callback(res);
    }
}

fn main() {
    let callback = |p: Ping| println!("{:?}", p);
    Handler::<Ping>::new(format!("{{\"ping\":\"{}\"}}", "abcdefg")).handle(callback);
}