Dotenv
Small, proc-macro crate that bakes environment variables from a .env file into the compiled binary. The dotenv!() macro is used the same as the built-in env!() macro, and the dotenv_option!() macro is used the same as option_env!().
Usage
.env file
FOO=BAR
In rust:
const FOO = dotenv!;
dotenv!("FOO") will expand at compile time to a &'static str of whatever FOO is set to in the .env file (in this case "bar").