test1.go

package main

import "fmt"

type Foo struct {
	Payload string
}

type Bar struct {
	Foo
}

func (f *Foo) DoStuff(arg string) {
	f.Payload = arg
}

func main() {
	f := &Bar{Foo{"1234"}}
	f.DoStuff("4321")
	fmt.Println(f)
}

test2.go

package main

import "fmt"

func call(f func(string)) { f("foo") }

type Foo struct {
	Payload string
}

func (f Foo) foo(str string) {
	fmt.Println(f.Payload, str)
}

func main() {
	f1 := Foo{"foo1"}
	f2 := Foo{"foo2"}
	call(f1.foo)
	call(f2.foo)
}