feat: change void to use interface{}

structure/void.go

@@ -1,4 +1,4 @@
 package structure
 
 // denoting no value for generic
-type Void struct{}
+type Void = interface{}

structure/void_test.go

@@ -0,0 +1,28 @@
+package structure_test
+
+import (
+	"testing"
+
+	"github.com/hjwalt/runway/structure"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestVoidCast(t *testing.T) {
+	assert := assert.New(t)
+
+	var voidValue structure.Void
+
+	voidValue = 1
+	assert.Equal(voidValue, 1)
+
+	intValue := 2
+	voidValue = structure.Void(intValue)
+	assert.Equal(voidValue, 2)
+
+	castTest, castSuccessful := voidValue.(int)
+	assert.Equal(castTest, 2)
+	assert.True(castSuccessful)
+
+	voidValue = "string"
+	assert.Equal(voidValue, "string")
+}