Why Does My Go http.FileServer Serve Outdated Files After Modification?

http.FileServer Behavior: Cache Invalidation for Edited Files

The http.FileServer package in Go provides a convenient way to serve static files, but users have encountered issues with caching that can lead to outdated content being returned after file modifications.

Problem Description

A simplified example demonstrates the issue: serving a static HTML page using http.FileServer. When the page is modified and reloaded, the browser receives the old version despite seeing the correct Content-Length in the response headers.

Troubleshooting

Independent variables were ruled out:

• Tested on multiple operating systems (Windows, Ubuntu, macOS)
• Verified file caching is not performed on disk

Solution

After careful investigation, the issue was identified:

Issue: Using a Virtual Box shared folder to host the static files

Reason: Virtualization introduces a layer of indirection that can interfere with file modification detection.

Fix:

To resolve the issue, it is recommended to physically copy the static files to the server's local filesystem instead of using a shared folder.

By eliminating the use of shared folders, http.FileServer can accurately detect file modifications and serve the updated content.

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