Golang type interface implementation (protocol of Swift)

protocols.go

package main

import "fmt"

// protocol

type Specimen interface {
	NumLegs() int
}
var Species = []Specimen{}

// implementation

type Human struct{}
func (h Human) NumLegs() int {
	return 2
}

type Cat struct{}
func (c Cat) NumLegs() int {
	return 4
}

func init() {
	Species = append(Species, Human{})
	Species = append(Species, Cat{})
}

func main() {
	fmt.Print("Registered species: ")
	fmt.Println(len(Species))
	
	fmt.Println("Number of legs of each: ")
	for _, specimen := range Species {
		fmt.Println(specimen.NumLegs())
	}
}