How Can I Embed Files into Go Binaries Using `go:embed` and `go generate`?

Embedding Files into Go Binaries

In programming, it is common to distribute executable files that require additional resources, such as text files. To simplify deployment and avoid having to distribute multiple files, it is beneficial to embed these resources within the binary itself.

Embedding Files with go:embed (Go 1.16 and later)

With Go 1.16, the go:embed directive provides a straightforward method for embedding files:

package main

import "embed"

// Embed the "hello.txt" file as a string
//go:embed hello.txt
var s string

// Embed the "hello.txt" file as a byte slice
//go:embed hello.txt
var b []byte

// Embed the "hello.txt" file as an embed.FS object
//go:embed hello.txt
var f embed.FS

func main() {
    // Read the file contents as a string
    data, _ := f.ReadFile("hello.txt")
    println(string(data))
}

Embedding Files with go generate (Before Go 1.16)

For earlier versions of Go, go generate offers an alternative approach:

1. Create an includetxt.go script: This script will read the text files and generate string literals for them.
2. Add the go:generate comment to main.go: The comment will trigger the execution of the includetxt.go script and generate the string literals.

3. Example code:

   main.go

   package main
   
   import "fmt"
   
   //go:generate go run scripts/includetxt.go
   
   func main() {
       fmt.Println(a)
       fmt.Println(b)
   }

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   scripts/includetxt.go

   package main
   
   import (
       "io"
       "io/ioutil"
       "os"
       "strings"
   )
   
   // Embed all .txt files as string literals
   func main() {
       fs, _ := ioutil.ReadDir(".")
       out, _ := os.Create("textfiles.go")
   
       for _, f := range fs {
           if strings.HasSuffix(f.Name(), ".txt") {
               out.WriteString(strings.TrimSuffix(f.Name(), ".txt") + " = `")
               f, _ := os.Open(f.Name())
               io.Copy(out, f)
               out.WriteString("`\n")
           }
       }
   }

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4. Compilation:

   $ go generate
   $ go build -o main

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Additional Notes:

• The go generate approach requires the text files to be UTF-8 encoded.
• For non-UTF-8 files, you can use custom encoding in the includetxt.go script.
• The embed.FS type in go:embed provides access to the embedded files using a virtual file system.

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