Go basically says, "if ANY type implements these functions with these signatures, it's a member of this interface."
Yes, this is I think the most innovative aspect of Go interfaces, and one of Go's best features. It's duck typing in a statically type-checked language. It avoids Java's problem of tagging classes with long lists of interfaces that they implement.
Well, from what I understand, Go has a separation between "interface" and "implementation", correct?
Given the above property there isn't really an implementation anymore. Individual types just have to implement the right functions, but that isn't really a blob of code to implement any single interface.