Unsubscribe middle closure function

[RelicOfTesla]

import (
	"github.com/asaskevich/EventBus"
	"github.com/stretchr/testify/require"
	"testing"
)

func TestAsaskevichBus_UnsubscribeClosureMiddle(t *testing.T) {

	callCount := 0
	sum := 0
	makeFn := func(a int) func() {
		return func() {
			callCount++
			sum += a
		}
	}
	const evName = "ev1"
	evBus := EventBus.New()
	f1 := makeFn(11)
	f2 := makeFn(22)
	f3 := makeFn(33)
	require.NoError(t, evBus.Subscribe(evName, f1))
	require.NoError(t, evBus.Subscribe(evName, f2))
	require.NoError(t, evBus.Subscribe(evName, f3))
	//
	require.NoError(t, evBus.Unsubscribe(evName, f2))
	//
	evBus.Publish(evName)
	require.Equal(t, callCount, 2)
	require.Equal(t, sum, 11+33)

}

like #47