Usage and examples of common Golang standard libraries

Golang commonly used standard library introduction and examples

Golang (also known as Go) is a programming language that uses concise syntax and efficient performance. As an open source language, its standard library provides many useful features that can save us time and effort during the development process. In this article, we will introduce some commonly used Golang standard libraries and provide corresponding sample code.

1. fmt standard library

fmt standard library provides formatting operations for input and output. It contains various methods, such as Println, Printf, and Sprintf, for printing to standard output or a string.

Sample code:

package main

import "fmt"

func main() {
    name := "World"
    fmt.Println("Hello", name)
    fmt.Printf("The value of pi is %f
", 3.1415)
    result := fmt.Sprintf("The square of 5 is %d", 5*5)
    fmt.Println(result)
}

2. os standard library

The os standard library provides the function of interacting with the operating system. It contains many methods, such as operating files, environment variables and command line parameters.

Sample code:

package main

import (
    "fmt"
    "os"
)

func main() {
    file, err := os.Open("test.txt")
    if err != nil {
        fmt.Println("File can't be opened:", err)
        return
    }
    defer file.Close()
    
    stat, err := file.Stat()
    if err != nil {
        fmt.Println("File can't be read:", err)
        return
    }
    fmt.Println("File size:", stat.Size())
}

3. net/http standard library

The net/http standard library provides the implementation of HTTP client and server. It allows us to create HTTP requests, listen on ports, and handle HTTP requests.

Sample code:

package main

import (
    "fmt"
    "net/http"
)

func main() {
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        fmt.Fprint(w, "Hello World")
    })

    http.ListenAndServe(":8080", nil)
}

4. encoding/json standard library

encoding/json standard library is used for encoding and decoding JSON. It provides methods such as Marshal and Unmarshal, making it very convenient to operate JSON data in Golang.

Sample code:

package main

import (
    "encoding/json"
    "fmt"
)

type Person struct {
    Name string `json:"name"`
    Age  int    `json:"age"`
}

func main() {
    jsonStr := `{"name":"John", "age":30}`
    
    var p Person
    if err := json.Unmarshal([]byte(jsonStr), &p); err != nil {
        fmt.Println("JSON parsing error:", err)
        return
    }
    fmt.Println(p.Name, p.Age)
    
    p.Age = 31
    data, err := json.Marshal(p)
    if err != nil {
        fmt.Println("JSON encoding error:", err)
        return
    }
    fmt.Println(string(data))
}

The above is only a small part of the Golang standard library. In fact, there are many other powerful functions that can be achieved through the standard library. By learning and using these standard libraries, we can write Golang programs more efficiently and implement various functions quickly. If you are interested in Golang, I encourage you to continue to dig into these standard libraries and try to use them. I wish you success in your learning and development!

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