How can Go's CookieJar be used to follow redirects while preserving cookies?

Leveraging Go's cookiejar to Follow Redirections with Cookies

When an HTTP request results in a 302 redirect, it's crucial to maintain cookies received from the server for the subsequent request. In Go, this can be achieved through the cookiejar package, providing a convenient way to automatically follow redirections while preserving cookies.

In this scenario, the goal is to emulate the behavior of CURL with the following settings:

• COOKIEFILE = "": Disable writing cookies to disk.
• AUTOREFERER = 1: Automatically set the Referer header.
• FOLLOWLOCATION = 1: Follow redirects.

Implementation with cookiejar

With Go 1.1, the net/http/cookiejar package is available to handle these tasks seamlessly. Here's a code sample demonstrating its usage:

<code class="go">package main

import (
    "golang.org/x/net/publicsuffix"
    "io/ioutil"
    "log"
    "net/http"
    "net/http/cookiejar"
)

func main() {
    // Configure the cookie jar.
    options := cookiejar.Options{
        PublicSuffixList: publicsuffix.List,
    }
    jar, err := cookiejar.New(&options)
    if err != nil {
        log.Fatal(err)
    }

    // Create an HTTP client with the cookie jar.
    client := http.Client{Jar: jar}

    // Make the request.
    resp, err := client.Get("http://dubbelboer.com/302cookie.php")
    if err != nil {
        log.Fatal(err)
    }

    // Read the response body.
    data, err := ioutil.ReadAll(resp.Body)
    resp.Body.Close()
    if err != nil {
        log.Fatal(err)
    }

    // Log the response.
    log.Println(string(data))
}</code>

In this example, the cookie jar is configured to follow the public suffix list, ensuring proper domain-based cookie handling. The client is created with the jar, and a GET request is made to the specified URL. The response body is read and logged, demonstrating that the cookie jar effectively handles the redirection and preserves the cookie.

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