added defer nil func example

defer/main.go

@@ -0,0 +1,17 @@
+package main
+
+import "fmt"
+
+// Sample code is taken from online tutorial https://blog.learngoprogramming.com/gotchas-of-defer-in-go-1-8d070894cb01
+// it demostrate all the common GOTCHA when using defer.
+
+// If a deferred func evaluates to nil, execution panic when surrounding func ends not when defer is called
+func nilFuncDefer() {
+	var run func() = nil
+	defer run()
+	fmt.Println("runs")
+}
+
+func main() {
+	nilFuncDefer()
+}