add export demo and test

_demo/go/export/c/c.go

@@ -0,0 +1,29 @@
+package C
+
+// XType - struct for export.go to use
+type XType struct {
+	ID    int32   `json:"id"`
+	Name  string  `json:"name"`
+	Value float64 `json:"value"`
+	Flag  bool    `json:"flag"`
+}
+
+func XAdd(a, b int) int {
+	return a + b
+}
+
+func Sub(a, b int64) int64 {
+	return a - b
+}
+
+func sub(a, b uint32) uint32 {
+	return a - b
+}
+
+func Xmul(a, b float32) float32 {
+	return a * b
+}
+
+func Concat(a, b string) string {
+	return a + b
+}