🔧 build: 使用 2021 版本

Author: wtklbm

Cargo.toml

@@ -5,7 +5,7 @@ authors = ["wtklbm <[email protected]>"]
 description = "crm can help you easy and fast switch between different cargo registries, now include: sjtu, tuna, ustc, rsproxy, bfsu, nju, hit."
 homepage = "https://github.com/wtklbm/crm"
 repository = "https://github.com/wtklbm/crm.git"
-edition = "2018"
+edition = "2021"
 license = "MIT OR Apache-2.0"
 keywords = ["cargo", "registry"]
 exclude = [".vscode/**"]