[mastax]

I remember a Rust AWS library worked like you describe (An old version of rusoto, I think, deprecated now).

I wasn't familiar with how AWS credentials are usually managed so I was very confused why I had to make my own struct and implement the `CredentialSource` trait on it. It felt like I was missing something... because I was. You're not supposed to enter the credentials directly, you're supposed to use the built-in EnvCredentialSource or whatever.