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