go-signature-sample

package main
 
import (
    "crypto/hmac"
    "crypto/sha256"
    "encoding/base64"
    "fmt"
    "strings"
)
 
const CLIENT_ID = "Client-Id"
const REQUEST_ID = "Request-Id"
const REQUEST_TIMESTAMP = "Request-Timestamp"
const REQUEST_TARGET = "Request-Target"
const DIGEST = "Digest"
const SYMBOL_COLON = ":"
 
// Generate Digest
func generateDigest(jsonBody string) string {
    converted := []byte(jsonBody)
    hasher := sha256.New()
    hasher.Write(converted)
    return (base64.StdEncoding.EncodeToString(hasher.Sum(nil)))
     
}

func generateSignature(clientId string, requestId string, requestTimestamp string, requestTarget string, digest string, secret string) string {
    // Prepare Signature Component
    fmt.Println("----- Component Signature -----")
    var componentSignature strings.Builder
    componentSignature.WriteString(CLIENT_ID + SYMBOL_COLON + clientId)
    componentSignature.WriteString("\n")
    componentSignature.WriteString(REQUEST_ID + SYMBOL_COLON + requestId)
    componentSignature.WriteString("\n")
    componentSignature.WriteString(REQUEST_TIMESTAMP + SYMBOL_COLON + requestTimestamp)
    componentSignature.WriteString("\n")
    componentSignature.WriteString(REQUEST_TARGET + SYMBOL_COLON + requestTarget) 
    componentSignature.WriteString("\n")
    componentSignature.WriteString(DIGEST + SYMBOL_COLON +digest) 
    // If body not send when access API with HTTP method GET/DELETE
    if len(digest) > 0  {
        componentSignature.WriteString("\n")
        componentSignature.WriteString(DIGEST + SYMBOL_COLON +digest)
    }
 
    fmt.Println(componentSignature.String())
    fmt.Println("")
 
    // Calculate HMAC-SHA256 base64 from all the components above
    key := []byte(secret)
    h := hmac.New(sha256.New, key)
    h.Write([]byte(componentSignature.String()))
    signature := base64.StdEncoding.EncodeToString(h.Sum(nil))
    // Prepend encoded result with algorithm info HMACSHA256=
    return "HMACSHA256="+signature
}

// Sample of Usage
func main() {
  
    // Genreate Digest from JSON Body
    var jsonBody = '{\"order\":{\"invoice_number\":\"INV-20210124-0001\",\"amount\":150000},\"virtual_account_info\":{\"expired_time\":60,\"reusable_status\":false,\"info1\":\"Merchant Demo Store\"},\"customer\":{\"name\":\"Taufik Ismail\",\"email\":\"taufik@example.com\"}}'
    digest := generateDigest(jsonBody);
    fmt.Println("----- Digest -----")
    fmt.Println(digest)
    fmt.Println("")
    
    // Generate Signature
    headerSignature := generateSignature(
        "yourClientId",
        "yourRequestId",
        "2020-10-21T03:38:28Z",
        "/request-target/goes-here", // For merchant request to DOKU, use DOKU path here. For HTTP Notification, use merchant path here
        digest, // Set empty string for this argumentes if HTTP Method is GET/DELETE
        "secret-key-from-DOKU-back-office")
 
    fmt.Println("----- Header Signature -----")    
    fmt.Println(headerSignature)
}