How to implement cookies in golang

In web development, cookies are a very common technology used to store some information about the user for use in subsequent requests.

Go language (golang) also provides complete cookie support, which can easily read and set cookies in HTTP requests and responses.

This article will introduce how golang implements cookies and provide some sample code so that readers can better understand. The following is a detailed introduction.

1. Cookies in golang

In golang, the Cookie type of the http package is used to represent a cookie. A cookie contains two fields: Key and Value, as well as some optional fields, such as Path, Domain, MaxAge, Expires, etc.

The following is the definition of Cookie:

type Cookie struct {

Name       string
Value      string
Path       string
Domain     string
Expires    time.Time
RawExpires string

MaxAge   int
Secure   bool
HttpOnly bool

Raw string
Unparsed []string

}

The meaning of each field of Cookie is as follows:

• Name: The name of the cookie
• Value: The value of the cookie
• Path: The valid request URL path of the cookie
• Domain: The host name of the valid request URL of the cookie
• Expires: The expiration time of the cookie
• MaxAge: The expiration time of the cookie, in seconds
• Secure: The cookie is only transmitted in HTTPS connections
• HttpOnly : The cookie cannot be accessed by JavaScript
• Raw: The original string of the cookie in the HTTP request
• Unparsed: The unprocessed cookie string

2. Set cookies

In golang, to set a cookie, you can use the SetCookie function of the http package. The SetCookie function requires a parameter of type ResponseWriter, which is used to send an HTTP response to the client.

The following is the definition of the SetCookie function:

func SetCookie(w ResponseWriter, cookie *Cookie)

In the sample code, we will set a name named "username" cookie and set its value to "john".

The sample code is as follows:

package main

import (

"net/http"

)

func main() {

http.HandleFunc("/", handler)
http.ListenAndServe(":8080", nil)

}

func handler(w http.ResponseWriter, r *http.Request) {

c := http.Cookie{Name: "username", Value: "john"}
http.SetCookie(w, &c)

}

3. Read cookie

In In golang, to read a cookie, you can use the Cookies function of the http package. The Cookies function requires a parameter of type Request, which is used to represent HTTP requests.

The following is the definition of the Cookies function:

func Cookies(r Request) []Cookie

In the sample code, we will read before Sets a cookie named "username" and prints its value to the console.

The sample code is as follows:

package main

import (

"fmt"
"net/http"

)

func main() {

http.HandleFunc("/", handler)
http.ListenAndServe(":8080", nil)

}

func handler(w http.ResponseWriter, r *http.Request) {

c, err := r.Cookie("username")
if err != nil {
    fmt.Println("Unable to read cookie")
} else {
    fmt.Println(c.Value)
}

}

This sample code uses the Cookie method of Request to read A cookie named "username". If the read is successful, the cookie value is output; otherwise, an error message is output.

Summary

This article introduces how to use cookies in golang, including how to create and read cookies. Through the introduction of this article, readers can master the basic usage of cookies in golang, providing more possibilities for web development.

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