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