golang中的//！+ //！-这些标记是什么？

Question

I am reading The Go Programming Language, and while browsing the source code I find certain tags, like:

//!+
//!-

or

//!+main
//!-main

Do they mean something to the compiler?

Answer 1

No, those comments don't mean something to the Go compiler. As stated in the gopl.io project's README.md:

Many of the programs contain comments of the form //!+ and //!-. These comments bracket the parts of the programs that are excerpted in the book; you can safely ignore them. In a few cases, programs have been reformatted in an unnatural way so that they can be presented in stages in the book.

For instance all code between the two snippets //!+bytecounter and //!-bytecounter are in the gopl.io/ch7/bytecounter snippet shown on p. 173 of the book.