feat: add __concurrent/arc-swap

__concurrent/arc-swap/Cargo.lock

@@ -0,0 +1,21 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "arc-swap"
+version = "0.1.0"
+dependencies = [
+ "arc-swap 0.4.7",
+ "once_cell",
+]
+
+[[package]]
+name = "arc-swap"
+version = "0.4.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4d25d88fd6b8041580a654f9d0c581a047baee2b3efee13275f2fc392fc75034"
+
+[[package]]
+name = "once_cell"
+version = "1.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "260e51e7efe62b592207e9e13a68e43692a7a279171d6ba57abd208bf23645ad"

__concurrent/arc-swap/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "arc-swap"
+version = "0.1.0"
+authors = ["Hatter Jiang <jht5945@gmail.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+arc-swap = "0.4"
+once_cell = "1.4"
+
+

__concurrent/arc-swap/src/main.rs

@@ -0,0 +1,11 @@
+use once_cell::sync::Lazy;
+use arc_swap::ArcSwap;
+
+static TEST_STRING: Lazy<ArcSwap<String>> = Lazy::new(|| {
+    ArcSwap::from_pointee("Hello World!".to_owned())
+});
+
+fn main() {
+    let s = TEST_STRING.load();
+    println!("{}", s);
+}