temp.go

package main

import (
	"log"
)

type Foo interface {
	Bar() string
}

type FooFactory func() Foo

type A struct {
	bar string
}

func NewA() *A {
	return &A{bar: "hello"}
}

func (a *A) Bar() string {
	return a.bar
}

type B struct {
	baz string
}

func NewB() *B {
	return &B{baz: "world"}
}

func (b *B) Bar() string {
	return b.baz
}

func Printer(fac FooFactory) {
	log.Println(fac().Bar())
}

func main() {
	Printer(NewA) //cannot use NewA (type func() *A) as type FooFactory in argument to Printer
	Printer(NewB) //cannot use NewB (type func() *B) as type FooFactory in argument to Printer
}