Example of idiomatic Go polymorphism

polymorphism.go

package main

import (
	"fmt"
)

type Named struct {
	name string
}

type Connection struct {
	Named
	database string
}

type Closeable interface {
	close() string
}

func (c Connection) close() string {
	return fmt.Sprintf("Closing connection %v", c.name)
}

type File struct {
	Named
	opener string
}

func (f File) close() string {
	return fmt.Sprintf("Closing %v", f.name)
}

func showClosing(c Closeable) string {
	return c.close()
}

func main() {
	connection := Connection{Named{name: "MyConnection"}, "PostgreSQL"}
	file := File{Named{name: "file.txt"}, "TextEdit"}
	fmt.Println(showClosing(connection))
	fmt.Println(showClosing(file))
}