use OnceLock from std instead of the once_cell crate (#349)

https://blog.rust-lang.org/2023/06/01/Rust-1.70.0.html#oncecell-and-oncelock

Cargo.toml

@@ -9,7 +9,6 @@ rust-version = "1.62"
 
 [dependencies]
 thiserror = "1.0"
-once_cell = "1.16"
 aho-corasick = "1.0"
 atom_syndication = "0.12"
 chrono = "0.4"

src/bot/telegram_client.rs

@@ -13,12 +13,12 @@ use frankenstein::Update;
 use isahc::prelude::*;
 use isahc::HttpClient;
 use isahc::Request;
-use once_cell::sync::OnceCell;
 use std::collections::VecDeque;
 use std::path::PathBuf;
+use std::sync::OnceLock;
 use typed_builder::TypedBuilder;
 
-static API: OnceCell<Api> = OnceCell::new();
+static API: OnceLock<Api> = OnceLock::new();
 
 #[derive(Clone, Debug)]
 pub struct Api {

src/db.rs

@@ -3,7 +3,7 @@ use chrono::prelude::*;
 use chrono::{DateTime, Utc};
 use diesel::pg::PgConnection;
 use diesel::r2d2;
-use once_cell::sync::OnceCell;
+use std::sync::OnceLock;
 
 #[cfg(test)]
 use diesel::connection::Connection;
@@ -15,7 +15,7 @@ pub mod feed_items;
 pub mod feeds;
 pub mod telegram;
 
-static POOL: OnceCell<r2d2::Pool<r2d2::ConnectionManager<PgConnection>>> = OnceCell::new();
+static POOL: OnceLock<r2d2::Pool<r2d2::ConnectionManager<PgConnection>>> = OnceLock::new();
 
 #[cfg(test)]
 pub fn establish_test_connection() -> PgConnection {

src/http_client.rs

@@ -2,10 +2,10 @@ use crate::config::Config;
 use isahc::config::RedirectPolicy;
 use isahc::prelude::*;
 use isahc::HttpClient;
-use once_cell::sync::OnceCell;
+use std::sync::OnceLock;
 use std::time::Duration;
 
-static CLIENT: OnceCell<HttpClient> = OnceCell::new();
+static CLIENT: OnceLock<HttpClient> = OnceLock::new();
 
 pub fn client() -> &'static HttpClient {
     CLIENT.get_or_init(init_client)