This makes all internal modules private, and only exposes a bunch of
public structs.
To fix your code, where it says “struct `...` is private”, just remove
preceding module name, for example:
```
examples/consumer.rs:4:5: 4:27 error: struct `Session` is private
examples/consumer.rs:4 use amqp::session::Session;
```
change line to:
```
use amqp::Session;
```