Book Image

Mastering Go – Third Edition - Third Edition

By : Mihalis Tsoukalos
5 (2)
Book Image

Mastering Go – Third Edition - Third Edition

5 (2)
By: Mihalis Tsoukalos

Overview of this book

Mastering Go is the essential guide to putting Go to work on real production systems. This freshly updated third edition includes topics like creating RESTful servers and clients, understanding Go generics, and developing gRPC servers and clients. Mastering Go was written for programmers who want to explore the capabilities of Go in practice. As you work your way through the chapters, you’ll gain confidence and a deep understanding of advanced Go concepts, including concurrency and the operation of the Go Garbage Collector, using Go with Docker, writing powerful command-line utilities, working with JavaScript Object Notation (JSON) data, and interacting with databases. You’ll also improve your understanding of Go internals to optimize Go code and use data types and data structures in new and unexpected ways. This essential Go programming book will also take you through the nuances and idioms of Go with exercises and resources to fully embed your newly acquired knowledge. With the help of Mastering Go, you’ll become an expert Go programmer by building Go systems and implementing advanced Go techniques in your projects.
Table of Contents (17 chapters)
14
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15
Index

The semaphore package

This last section of this chapter presents the semaphore package, which is provided by the Go team. A semaphore is a construct that can limit or control the access to a shared resource. As we are talking about Go, a semaphore can limit the access of goroutines to a shared resource but originally, semaphores were used for limiting access to threads. Semaphores can have weights that limit the number of threads or goroutines that can have access to a resource.

The process is supported via the Acquire() and Release() methods, which are defined as follows:

func (s *Weighted) Acquire(ctx context.Context, n int64) error
func (s *Weighted) Release(n int64)

The second parameter of Acquire() defines the weight of the semaphore.

As we are going an external package, we need to put the code inside ~/go/src in order to use Go modules: ~/go/src/github.com/mactsouk/semaphore. Now, let us present the code of semaphore.go, which shows an implementation of...