Master Golang: Embed Directive

//go:embed is a compiler directive that allows programs to include arbitrary files and folders in the Go binary at build time. Read more about the embed directive here.

 
package main

Import the embed package; if you don’t use any exported identifiers from this package, you can do a blank import with _ "embed".

 
import (
    "embed"
)

embed directives accept paths relative to the directory containing the Go source file. This directive embeds the contents of the file into the string variable immediately following it.

 
//go:embed folder/single_file.txt
var fileString string

Or embed the contents of the file into a []byte.

 
//go:embed folder/single_file.txt
var fileByte []byte

We can also embed multiple files or even folders with wildcards. This uses a variable of the embed.FS type, which implements a simple virtual file system.

 
//go:embed folder/single_file.txt
//go:embed folder/*.hash
var folder embed.FS

func main() {

Print out the contents of single_file.txt.

 
    print(fileString)
    print(string(fileByte))

Retrieve some files from the embedded folder.

 
    content1, _ := folder.ReadFile("folder/file1.hash")
    print(string(content1))

    content2, _ := folder.ReadFile("folder/file2.hash")
    print(string(content2))
}

Use these commands to run the example. (Note: due to limitation on go playground, this example can only be run on your local machine.)

 
$ mkdir -p folder
$ echo "hello go" > folder/single_file.txt
$ echo "123" > folder/file1.hash
$ echo "456" > folder/file2.hash
 
$ go run embed-directive.go
hello go
hello go
123
456

Next example: Testing and Benchmarking.

Gratitude to Mark McGranaghan and Eli Bendersky