implements declarationOne of the least known or appreciated advantages of Go over languages like Java and C++ is that the development doesn’t have to know about an interface that it fulfills. In fact, often a struct might end up fulfilling an interface without even knowing it.
Take the fmt.Stringer interface, for example. Just add a String() string method and boom, you are done. Your struct can now be passed into anything that accepts a Stringer type (and there are vary many things that do). Now imagine doing that same thing in Java. Every single class would have to include implements Stringer along with the dozens of other interfaces. Go does require that at all.
This design decision is one of those subtle but substantial points of objective evidence that Go was designed to be amazing, not some accidental success. The entire idiomatic approach to interfaces is absolutely brilliant, but only experienced polyglot developers (who have been burned by all the alternatives) will even notice advantages such as this.