在根据这个文档学习时 https://kaisery.github.io/trpl-zh-cn/ch07-01-mod-and-the-filesystem.html https://kaisery.github.io/trpl-zh-cn/ch07-02-controlling-visibility-with-pub.html

在第二篇文章中加入 extern crate communicator; 后，在编译的时候提示如下： warning: custom registry support via the registry.index configuration is being removed, this functionality will not work in the future Compiling test2 v0.1.0 (file:///home/liuwenling/project/test2) error[E0463]: can't find crate for communicator --> src/main.rs:1:1 | 1 | extern crate communicator; | ^^^^^^^^^^^^^^^^^^^^^^^^^^ can't find crate

error: aborting due to previous error

error: Could not compile test2.

请问中间是不是漏掉了什么步骤？？