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
Other Books You May Enjoy
15
Index

Writing to a file

So far, we have seen ways to read files. This subsection shows how to write data to files in four different ways and how to append data to an existing file. The code of writeFile.go is as follows:

package main
import (
    "bufio"
    "fmt"
    "io"
    "os"
)
func main() {
    buffer := []byte("Data to write\n")
    f1, err := os.Create("/tmp/f1.txt")

os.Create() returns an *os.File value associated with the file path that is passed as a parameter. Note that if the file already exists, os.Create() truncates it.

    if err != nil {
        fmt.Println("Cannot create file", err)
        return
    }
    defer f1.Close()
    fmt.Fprintf(f1, string(buffer))

The fmt.Fprintf() function, which requires a string variable, helps you write data to your own files using the format you want. The only requirement is having an io.Writer to write to. In this case, a valid *os.File variable,...