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: storageTokenEncryptor.go
    path of file: ./repos/acra/pseudonymization/storage
    
    the code of the file until where you have to start completion: /*
Copyright 2020, Cossack Labs Limited

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under th
    
func (s *scellEncryptor) Encrypt(data []byte, ctx common.TokenContext) ([]byte, error) {
	var context []byte
	var key []byte
	var err error
	// TODO decide what to do
	if len(ctx.AdditionalContext) != 0 {
		context = ctx.AdditionalContext
	} else {
		context = ctx.ClientID
	}
	key, err = s.tokenKeystore.GetClientIDSymmetricKey(ctx.ClientID)
	if err != nil {
		return nil, err
	}
	encrypted, err := acrablock.CreateAcraBlock(data, key, context)
	utils.ZeroizeSymmetricKey(key)

	return encrypted, err
}