Go embed
last modified August 24, 2023
Go embed tutorial shows how to access embedded files from within a running Go program.
The embed package allows to access static files such as images
and HTML files from within a running Go binary. It was introduced in Go 1.16.
$ go version go version go1.18.1 linux/amd64
We use Go version 1.18.
Go embed a text file
In the first example, we embed a text file into a slice of bytes.
sky blue rock water array karma falcon
We have a few words in the text file.
package main
import (
"bytes"
_ "embed"
"fmt"
)
var (
//go:embed data/words.txt
data []byte
)
func main() {
fmt.Println(string(data))
fmt.Println("----------------------")
words := bytes.Split(data, []byte{'\n'})
for _, w := range words {
fmt.Println(string(w))
}
}
We embed a text file into the program and print the data.
var (
//go:embed data/words.txt
data []byte
)
Embedding is done by using the //go:embed directive above the
variable declaration.
$ go build $ ./txtfile.exe sky blue rock water array karma falcon ---------------------- sky blue rock water array karma falcon
Go embed multiple files
In the following example, we embed two text files.
Perl Raku F# Clojure Go C#
This is the langs.txt file.
sky blue rock falcon war tree storm cup
This is the words.txt file.
package main
import (
"embed"
"fmt"
)
//go:embed data/*
var f embed.FS
func main() {
langs, _ := f.ReadFile("data/langs.txt")
fmt.Println(string(langs))
words, _ := f.ReadFile("data/words.txt")
fmt.Println(string(words))
}
We embed two text files and print their contents.
//go:embed data/* var f embed.FS
With the * wildcard character, we embed all files within the data directory.
$ go build $ ./files.exe Perl Raku F# Clojure Go C# sky blue rock falcon war tree storm cup
Go embed static files
In the following example, we embed static files into a binary of a web application.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Home</title>
</head>
<body>
<p>
Home page
</p>
</body>
</html>
This is the index.html file.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>About</title>
</head>
<body>
<p>
About page
</p>
</body>
</html>
This is the about.html file.
package main
import (
"embed"
"io/fs"
"net/http"
)
//go:embed public
var content embed.FS
func handler() http.Handler {
fsys := fs.FS(content)
html, _ := fs.Sub(fsys, "public")
return http.FileServer(http.FS(html))
}
func main() {
mux := http.NewServeMux()
mux.Handle("/", handler())
http.ListenAndServe(":8080", mux)
}
The code example runs a server which serves two static files. We embed a whole directory.
//go:embed public var content embed.FS
The embed.FS allows to embed a tree of files.
func handler() http.Handler {
fsys := fs.FS(content)
html, _ := fs.Sub(fsys, "public")
return http.FileServer(http.FS(html))
}
The handler serves static files from the public directory. In Go,
the http.FileServer is used to serve static content.
In this article we have showed how to access static files from within a
running Go program using the embed package.
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