Go: Under the Hood

Current content is based on go1.26

Go has been around for more than a decade since its birth in 2009. Looking across the history of most programming languages, it is striking how little Go itself has changed over its decade of evolution: its users keep writing applications that stay backward compatible. From the standpoint of language design, for a language built from the start around the principles of low cost, high concurrency, and simplicity, it is hard not to be curious about the implementation mechanisms and the concrete workings behind that simple surface. This book discusses the technical principles in the Go source engineering and how they have evolved.

To the Reader

The reader may wonder: designs keep evolving and source keeps changing, so why spend effort studying source that one may never touch at work? The author thinks otherwise, because “software engineering happens the moment code is read by someone other than its original author.” In reading the source, beyond deepening our understanding of the language itself, what matters more is grasping the fundamental principles a design rests on, together with the engineering decisions, practices, and implementation techniques that others applied while building it. Code can always be rebuilt from scratch, but principles “live forever.”

The vision for this book is to cover every facet of the Go language. This includes the Go runtime components that user code touches directly, the toolchain tightly bound to key language features, many important standard libraries, and more. In some cases the book discusses implementation differences across platforms, with the focus on Linux/amd64.

Prerequisites

The reader should have some basic computer science literacy, having taken at least one course in programming and one in data structures, comfortable for instance discussing concepts such as hash tables and red-black trees. Basic knowledge of discrete mathematics and probability, with some understanding of predicates, random variables, and the like, will help with parts of the book.

The book does not assume that the reader already knows how to use Go, so it gives a quick tour of the Go language specification at the start. If you already have experience coding in Go, that will help you read the book.

About This Edition

The content of this book has been systematically rewritten and revised against Go 1.26, covering five parts: the panorama and history, language features, concurrency, memory, and the compiler and toolchain. Every section tries to return to the thread of “problem, design, evolution, trade-off, implementation,” cross-checked against the Go source and primary design documents.

Even so, the source keeps evolving, and the book is bound to contain omissions or material that goes stale across versions. If the reader suspects a passage is wrong, please open an Issue or a Pull Request in the repository, and we will keep revising.

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Community Support

Updates to the book and some additional references can be found on the book’s home page ( https://golang.design/under-the-hood ) and its GitHub repository ( https://github.com/golang-design/under-the-hood ). This is an open-source book created under the golang.design initiative. The reader can raise questions about the book’s content on GitHub, report errors, or even take part in the writing. The author welcomes Issues and Pull Requests on the repository; for the details please see how to contribute. If you would like to follow updates to this repository, click Watch. If you enjoy the book, we are also glad to receive your Star and your support.

Acknowledgments

The lead author (@changkun) first wishes to thank @yangwenmai, founder of Go 夜读, for sponsoring the golang.design initiative. We also wish to thank the core members of the Go 夜读 community group for the Go community environment they have worked to build, namely @qcrao, @eddycjy, @FelixSeptem, along with friends in the community who actively join and discuss Go-related questions, namely @cch123.

This book could not have been written without the support of many attentive readers. We have received helpful feedback and errata from, among others: @two, @yangxikun, @cnbailian, @choleraehyq, @PureWhiteWu, @hw676018683, @wangzeping722, @l-qing. We are sincerely grateful for their questions and corrections. Errors no doubt remain, and we welcome further corrections and feedback.

Finally, special thanks to @egonelbre for the Gopher artwork.