How to encrypt a value imported from a JSON file using SOPS (Secrets OPerationS) and Go?

Question

I have a JSON file as follows.

secret.json:

{
    "secret": "strongPassword"
}

I want to print out an encrypted value of the key "secret".

I've so far tried as follows.

package main

import (
    "encoding/json"
    "fmt"
    "io/ioutil"

    "go.mozilla.org/sops"
)

type secretValue struct {
    Value string `json:"secret"`
}

func main() {
    file, _ := ioutil.ReadFile("secret.json")
    getSecretValue := secretValue{}
    _ = json.Unmarshal([]byte(file), &getSecretValue)
    encryptedValue, err := sops.Tree.Encrypt([]byte(getSecretValue.Value), file)
    if err != nil {
        panic(err)
    }
    fmt.Println(encryptedValue)
}

As you might have guessed, I'm pretty new to Go and the code above doesn't work.

How can I improve the code to print out the encrypted value?

Please note that I'm writing code like this only to see how SOPS works using Go. I don't print out secret value like this in production.

Edit:

I think the problem is the arguments for the Encrypt function. According to the documentation, it should take []byte key and Cipher arguments, but I don't know either if I'm setting the []byte key correct or where that Cipher comes from. Is it from crypto/cipher package?

Edit 2:

Thank you @HolaYang for the great answer. I tried to make your answer work with the external JSON file as follows, but it gave me an error message saying cannot use fileContent (type secretValue) as type []byte in argument to (&"go.mozilla.org/sops/stores/json".Store literal).LoadPlainFile.

 package main

import (
    hey "encoding/json"
    "fmt"
    "io/ioutil"

    "go.mozilla.org/sops"
    "go.mozilla.org/sops/aes"
    "go.mozilla.org/sops/stores/json"
)

type secretValue struct {
    Value string `json:"secret"`
}

func main() {
    //  fileContent := []byte(`{
    //    "secret": "strongPassword"
    //    }`)
    file, _ := ioutil.ReadFile("secret.json")
    fileContent := secretValue{}
    //_ = json.Unmarshal([]byte(file), &fileContent)
    _ = hey.Unmarshal([]byte(file), &fileContent)
    encryptKey := []byte("0123456789012345") // length 16

    branches, _ := (&json.Store{}).LoadPlainFile(fileContent)
    tree := sops.Tree{Branches: branches}
    r, err := tree.Encrypt(encryptKey, aes.NewCipher())
    if err != nil {
        panic(err)
    }
    fmt.Println(r)
}

Answer 1

Let's see the function declaration of sops.Tree.Encrypt (a typo here in your code). By the code, we should do in these steps.

1. Construct a sops.Tree instance with the json file.
2. Use a certain Cipher for your encrypt.

Try yourself in this way please.

Code demo below, with AES as Cipher, and sops can only encrypt the total tree with the source code interface.

package main

import (
    "fmt"

    "go.mozilla.org/sops"
    "go.mozilla.org/sops/aes"
    "go.mozilla.org/sops/stores/json"
)

func main() {
    /*
    fileContent := []byte(`{
    "secret": "strongPassword"
    }`)
    */
    fileContent, _ := ioutil.ReadFile("xxx.json")

    encryptKey := []byte("0123456789012345") // length 16

    branches, _ := (&json.Store{}).LoadPlainFile(fileContent)
    tree := sops.Tree{Branches: branches}
    r, err := tree.Encrypt(encryptKey, aes.NewCipher())
    if err != nil {
        panic(err)
    }
    fmt.Println(r)
}