Will such a security system help?

Question

MySQL

Hello. I have all the security updates on the server, etc. But still, I'm afraid that if they get access to the database, they can do business (I have an online game. I got into the database, found myself and drew parameters for myself, and maybe my neighbors). I encrypt login and email using xxtea. The key is embedded in the source of the Golang project. There are only compiled binaries on the server. So without decompiling Go, you won't be able to find out your string.
That's what I have in the database
Or is it still a useless measure?
What else do you recommend?
Thank you all
UPD.
Doesn't affect performance. Encryption and decryption take 1 ms
pass and salt (sha512 + sha 256 + salt)

func userSave(result []string) bool {
  //result[0] = login
  //result[1] = email
  //result[2] = pass
  var salt string = newSalt()
  if salt == "err" {
    return false
  }
  var pass string = passwordHash(salt + result[2] + salt + result[1] + salt + result[1] + salt + result[2] + salt + result[0])

  res, err := DB.Exec("INSERT INTO users (login, email, pass,salt)VALUES(?,?,?,?)", string(xxtea.Encrypt([]byte(v.Trim(result[0])), X_secret)), string(xxtea.Encrypt([]byte(v.Trim(result[1])), X_secret)), pass, salt)

  if err != nil {
    print(err)
    return false
  }

  insertId, err := res.LastInsertId()

  if err != nil {
    print(err)
    return false
  }
  print(insertId)
  return true
}

func newSalt() string {
  rb := make([]byte, 64)
  _, err := rand.Read(rb)
  if err != nil {
    return "err"
  }

  return base64.URLEncoding.EncodeToString(rb)
}
func passwordHash(pass string) string {
  text := v.Trim(pass)
  hash := sha512.New()
  hash.Write([]byte(text))

  return1 := hex.EncodeToString(hash.Sum(nil))
  var i int = 0
  hashi := sha256.New()
  for i <= 10 {
    i = i + 1
    hashi.Write([]byte(return1))
    return1 = hex.EncodeToString(hashi.Sum(nil))
  }

  return return1
}

Answer 1

So without decompiling Go, you won't be able to find out your string.

it will lie openly in memory, if that.
In fact, all you need to do is to protect yourself from unauthorized connection to the database (even if it doesn’t look at the outside at all, close the ports), you also need to restrict access via SSH, or ban people who are breaking too hard, etc.
decoding what? password? Data? The password must be hashed (for example, bcrypt) so that it cannot be decrypted back.