docs: add missing import (#5500)

Author: lucasfcnunes

docs/registry/txt.md

@@ -115,37 +115,39 @@ In some cases you might need to edit registry TXT records. The following example
 package main
 
 import (
- "fmt"
- "sigs.k8s.io/external-dns/endpoint"
+	b64 "encoding/base64"
+	"fmt"
+
+	"sigs.k8s.io/external-dns/endpoint"
 )
 
 func main() {
- keys := []string{
-  "ZPitL0NGVQBZbTD6DwXJzD8RiStSazzYXQsdUowLURY=", // safe base64 url encoded 44 bytes and 32 when decoded
-  "01234567890123456789012345678901",             // plain txt 32 bytes
-  "passphrasewhichneedstobe32bytes!",             // plain txt 32 bytes
- }
-
- for _, k := range keys {
-  key := []byte(k)
-  if len(key) != 32 {
-   // if key is not a plain txt let's decode
-   var err error
-   if key, err = b64.StdEncoding.DecodeString(string(key)); err != nil || len(key) != 32 {
-    fmt.Errorf("the AES Encryption key must have a length of 32 byte")
-   }
-  }
-  encrypted, _ := endpoint.EncryptText(
-   "heritage=external-dns,external-dns/owner=example,external-dns/resource=ingress/default/example",
-   key,
-   nil,
-  )
-  decrypted, _, err := endpoint.DecryptText(encrypted, key)
-  if err != nil {
-   fmt.Println("Error decrypting:", err, "for key:", k)
-  }
-  fmt.Println(decrypted)
- }
+	keys := []string{
+		"ZPitL0NGVQBZbTD6DwXJzD8RiStSazzYXQsdUowLURY=", // safe base64 url encoded 44 bytes and 32 when decoded
+		"01234567890123456789012345678901",             // plain txt 32 bytes
+		"passphrasewhichneedstobe32bytes!",             // plain txt 32 bytes
+	}
+
+	for _, k := range keys {
+		key := []byte(k)
+		if len(key) != 32 {
+			// if key is not a plain txt let's decode
+			var err error
+			if key, err = b64.StdEncoding.DecodeString(string(key)); err != nil || len(key) != 32 {
+				fmt.Errorf("the AES Encryption key must have a length of 32 byte")
+			}
+		}
+		encrypted, _ := endpoint.EncryptText(
+			"heritage=external-dns,external-dns/owner=example,external-dns/resource=ingress/default/example",
+			key,
+			nil,
+		)
+		decrypted, _, err := endpoint.DecryptText(encrypted, key)
+		if err != nil {
+			fmt.Println("Error decrypting:", err, "for key:", k)
+		}
+		fmt.Println(decrypted)
+	}
 }
 ```