At the end of the day, whatever other dark magic is going on in our architecture, it will come down to some Go method being called, doing some work, and returning a result. So the next thing we are going to do is define and implement the Vault service itself.
Inside the vault folder, add the following code to a new service.go file:
// Service provides password hashing capabilities.
type Service interface {
Hash(ctx context.Context, password string) (string,
error)
Validate(ctx context.Context, password, hash string)
(bool, error)
}
This interface defines the service.
Tip
You might think that VaultService would be a better name than just Service, but remember that since this is a Go package, it will been seen externally as vault.Service, which reads nicely.
We define our two methods: Hash and Validate. Each takes context.Context as the first argument, followed by normal string arguments. The responses are normal Go types as well: string, bool, and error.