Interfaces vs Function Composition

my_test.go

package my_test

import "testing"

type AnInterface interface {
	Update() int
}

type ImplementsInterface struct {
}

func (a *ImplementsInterface) Update() int {
	return 0
}

func BenchmarkAnInterface(b *testing.B) {
	var target AnInterface
	target = &ImplementsInterface{}

	for i := 0; i < b.N; i++ {
		Run(target)
	}
}

func Run(target AnInterface) {
	target.Update()
}

type ComposedOfFunctions struct {
	Update func() int
}

func BenchmarkComposedOfFunctions(b *testing.B) {
	target := ComposedOfFunctions{
		Update: func() int {
			return 0
		},
	}

	for i := 0; i < b.N; i++ {
		RunFunc(target)
	}
}

func RunFunc(target ComposedOfFunctions) {
	target.Update()
}