How to Use Go's sync.Once for Single Execution Guarantees

Introduction
Prerequisites
Overview
Step 1: Installing Go
Step 2: Understanding sync.Once
Step 3: Using sync.Once in Your Code
Conclusion

Introduction

In concurrent programming, it is often necessary to guarantee that a certain section of code is executed only once across multiple goroutines. Go provides the sync.Once package to achieve this single execution guarantee efficiently. In this tutorial, we will explore the sync.Once package and learn how to use it effectively in Go programs. By the end of this tutorial, you will be able to implement safe and efficient single execution guarantees in your concurrent Go code.

Prerequisites

To follow along with this tutorial, you should have a basic understanding of Go programming language syntax and concurrency concepts. You should have Go installed on your system.

Overview

Learn about the purpose of the sync.Once package.
Understand how sync.Once works under the hood.
Use sync.Once to guarantee single execution of code.
Implement sync.Once in a practical example.

Step 1: Installing Go

Before we begin, make sure you have Go installed on your system. You can download and install Go from the official website: https://golang.org/dl/

Verify your Go installation by running the following command in your terminal:

go version

This should output the Go version you have installed.

Step 2: Understanding sync.Once

The sync.Once type in the sync package is used to perform a certain action only once, regardless of how many goroutines are accessing it. It provides a mechanism to initialize values, set up resources, or execute any critical code section that should not be repeated.

The basic syntax to create a sync.Once variable is as follows:

var once sync.Once

To ensure the code executes only once, sync.Once provides a method called Do, which takes a function as an argument. This function will be executed only once, even if multiple goroutines attempt to call Do simultaneously.

Step 3: Using sync.Once in Your Code

Let’s dive into an example to understand how to use sync.Once in practice. Consider a scenario where you want to initialize a global configuration object only once, regardless of how many goroutines access it. Here’s a step-by-step guide to achieving this using sync.Once.

Create a new file called main.go and open it in your preferred text editor.

Add the following import statement at the beginning of the file:

 package main
    
 import (
 	"fmt"
 	"sync"
 )

Declare a struct to represent our global configuration object:
```
 type Config struct {
 	// Configuration fields
 }
```
Declare a global variable of type Config:
```
 var config Config
```
Initialize the sync.Once variable:
```
 var once sync.Once
```

Define a function that will initialize our global configuration object:

 func initializeConfig() {
 	config = Config{
 		// Initialize configuration fields
 	}
 }

Create a function to access the global configuration object:

 func getConfig() Config {
 	once.Do(initializeConfig)
 	return config
 }

Finally, in the main function, use the getConfig function to access the configuration object:
```
 func main() {
 	fmt.Println(getConfig())
 }
```
Save the file and open a terminal.
Navigate to the directory containing the main.go file.
Build and run the Go program using the following command:
```
go run main.go
```
Congratulations! You have successfully used sync.Once to guarantee single execution of code. The initializeConfig function will be executed only once, regardless of how many times the getConfig function is called.

Conclusion

In this tutorial, you learned how to use Go’s sync.Once package to ensure that a section of code executes only once across multiple goroutines. You explored the steps to implement sync.Once in a practical example, allowing safe and efficient single execution guarantees in your Go programs. Now you can confidently utilize sync.Once to simplify concurrent initialization and other critical operations in your Go code.

Published: 24 July 2021