add one more project structure recommendation

_examples/project/pkg/http/handlers/cors.go

@@ -0,0 +1,28 @@
+package handlers
+
+import "github.com/kataras/iris/v12"
+
+// CORS set ups a cors allow-all.
+// We may need to edit it before deployment.
+func CORS(allowedOrigin string) iris.Handler { // or "github.com/iris-contrib/middleware/cors"
+	if allowedOrigin == "" {
+		allowedOrigin = "*"
+	}
+
+	return func(ctx iris.Context) {
+		ctx.Header("Access-Control-Allow-Origin", allowedOrigin)
+		ctx.Header("Access-Control-Allow-Credentials", "true")
+		// July 2021 Mozzila updated the following document: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Referrer-Policy
+		ctx.Header("Referrer-Policy", "no-referrer-when-downgrade")
+		ctx.Header("Access-Control-Expose-Headers", "*, Authorization, X-Authorization")
+		if ctx.Method() == iris.MethodOptions {
+			ctx.Header("Access-Control-Allow-Methods", "*")
+			ctx.Header("Access-Control-Allow-Headers", "*")
+			ctx.Header("Access-Control-Max-Age", "86400")
+			ctx.StatusCode(iris.StatusNoContent)
+			return
+		}
+
+		ctx.Next()
+	}
+}