You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: example_test.go
    path of file: ./repos/gccrs/libgo/go/crypto/cipher
    
    the code of the file until where you have to start completion: // Copyright 2012 The Go Author
    
func ExampleNewGCM_decrypt() {
	// Load your secret key from a safe place and reuse it across multiple
	// Seal/Open calls. (Obviously don't use this example key for anything
	// real.) If you want to convert a passphrase to a key, use a suitable
	// package like bcrypt or scrypt.
	// When decoded the key should be 16 bytes (AES-128) or 32 (AES-256).
	key, _ := hex.DecodeString("6368616e676520746869732070617373776f726420746f206120736563726574")
	ciphertext, _ := hex.DecodeString("c3aaa29f002ca75870806e44086700f62ce4d43e902b3888e23ceff797a7a471")
	nonce, _ := hex.DecodeString("64a9433eae7ccceee2fc0eda")

	block, err := aes.NewCipher(key)
	if err != nil {
		panic(err.Error())
	}

	aesgcm, err := cipher.NewGCM(block)
	if err != nil {
		panic(err.Error())
	}

	plaintext, err := aesgcm.Open(nil, nonce, ciphertext, nil)
	if err != nil {
		panic(err.Error())
	}

	fmt.Printf("%s\n", plaintext)
	// Output: exampleplaintext
}