Merge pull request #49 from awslabs/dev

upgrade to Rust 2021 edition

Author: bnusunny

Cargo.toml

@@ -2,7 +2,7 @@
 name = "aws-lambda-adapter"
 version = "0.3.2"
 authors = ["Harold Sun <[email protected]>"]
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 env_logger = "0.8.3"