Why Does http.FileServer Serve Outdated Files When Using Virtual Box Shared Folders?

Caching Issues with http.FileServer

This article addresses a specific challenge encountered while using the http.FileServer function in a Go application. The issue arises when the function caches file contents and continues to serve old versions even after the files have been edited.

In a simplified example, a Go program serves static HTML files from a ./www/ directory:

<code class="go">package main

import (
    "fmt"
    "net/http"
)

func main() {
    http.Handle("/", http.FileServer(http.Dir("./www/")))
    err := http.ListenAndServe(":8080", nil)
    if err != nil {
        fmt.Println(err)
    }
}</code>

However, after editing the HTML file and reloading the page, the browser continues to display the outdated content. The issue persists even after restarting the program.

Cause

The root of the problem lies in the use of a Virtual Box shared folder to host the HTML files. This configuration causes Windows to cache file contents, preventing the http.FileServer function from delivering the updated versions.

Solution

To resolve the issue, avoid using Virtual Box shared folders for files intended for use in http.FileServer. Instead, store the files directly on the host system, such as in a /testing/ directory:

<code class="go">http.Handle("/", http.FileServer(http.Dir("/home/vagrant/testing/")))</code>

By following this guideline, the http.FileServer function will accurately serve updated file contents without any caching issues.

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