How Can I Serve Static Files Directly from Memory in Go?

Serving Static Files from Memory in Go

In Go, the FileServer handler provides a convenient method for serving static files. However, for certain scenarios where the number of files is limited (e.g., two to three files), manually managing the deployment of these files can be cumbersome.

In-Memory File Serving

To alleviate the need for external file handling, we can explore the option of embedding static files into the binary and serving them directly from memory. One way to achieve this is through a custom file system implementation.

Custom File System Interface Implementation

The FileServer handler requires a FileSystem object, which typically represents the actual file system. However, we can create our own FileSystem implementation that operates solely in memory. The following code defines a simple in-memory file system:

package main

import (
    "net/http"
)

type InMemoryFS map[string]http.File

To interact with the file system, we implement the Open method, which returns an http.File object representing the file in memory:

func (fs InMemoryFS) Open(name string) (http.File, error) {
    if f, ok := fs[name]; ok {
        return f, nil
    }
    panic("No file")
}

In-Memory File Implementation

Next, we define an InMemoryFile type that implements the http.File interface:

type InMemoryFile struct {
    at   int64
    Name string
    data []byte
    fs   InMemoryFS
}

The InMemoryFile implementation provides methods for manipulating the file data, including Read, Seek, and Close.

Creating an In-Memory File Server

With the custom FileSystem and http.File implementation, we can create a FileServer that operates on the in-memory file system:

FS := make(InMemoryFS)
FS["foo.html"] = LoadFile("foo.html", HTML, FS)
FS["bar.css"] = LoadFile("bar.css", CSS, FS)
http.Handle("/", http.FileServer(FS))
http.ListenAndServe(":8080", nil)

This approach allows us to define static files as constants and serve them directly from memory, eliminating the need for external file management.

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