Dependency injection in Go via explicit type

typebound.go

package main

import "log"

type printerFunc func(message string, args ...interface{})

type demo struct {
	printer printerFunc
}

func (d *demo) hello(message string, args ...interface{}) {
	d.printer(message, args...)
}

func newDemo(printer printerFunc) *demo {
	return &demo{
		printer: printer,
	}
}

func main() {
	d := newDemo(log.Printf)
	d.hello("hello %s", "world")
}