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)
Other Books You May Enjoy

Closured variables and the go statement

In this section, we are going to talk about closured variables, which are variables inside closures, and the go statement. Notice that closured variables in goroutines are evaluated when the goroutine actually runs and when the go statement is executed in order to create a new goroutine. This means that closured variables are going to be replaced by their values when the Go scheduler decides to execute the relevant code. This is illustrated in the main() function of goClosure.go:

func main() {
    for i := 0; i <= 20; i++ {
        go func() {
            fmt.Print(i, " ")

Running goClosure.go produces the next output:

$ go run goClosure.go 
3 7 21 21 21 21 21 21 21 21 21 21 21 21 21 21 21 21 21 21 21

The program mostly prints the number 21, which is the last value of the variable of the for loop and not the other numbers. As i is a closured variable...