add IsClosed to UnitTest

Author: joesonw

go.mod

@@ -1,5 +1,7 @@
 module github.com/yuin/gopher-lua
 
+go 1.14
+
 require (
 	github.com/chzyer/logex v1.1.10 // indirect
 	github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e

state_test.go

@@ -7,6 +7,12 @@ import (
 	"time"
 )
 
+func TestLStateIsClosed(t *testing.T) {
+	L := NewState()
+	L.Close()
+	errorIfNotEqual(t, true, L.IsClosed())
+}
+
 func TestCallStackOverflowWhenFixed(t *testing.T) {
 	L := NewState(Options{
 		CallStackSize: 3,