[Go] Add imtype, goin, goout, godirectorin, and godirectorout

typemaps, to support writing Go code to convert between types.

Examples/test-suite/go_inout.i

@@ -0,0 +1,79 @@
+// Test the goin and goout typemaps.
+
+%module go_inout
+
+%{
+#include <string>
+%}
+
+%inline
+%{
+
+struct MyStruct {
+  std::string str;
+};
+
+struct RetStruct {
+  std::string str;
+};
+
+%}
+
+// Write a typemap that calls C++ by converting in and out of JSON.
+
+%go_import("encoding/json")
+
+%insert(go_header)
+%{
+
+type In json.Marshaler
+
+%}
+
+%typemap(gotype) MyStruct "In"
+
+%typemap(imtype) MyStruct "string"
+
+%typemap(goin) MyStruct
+%{
+	{
+		b, err := $input.MarshalJSON()
+		if err != nil {
+			panic(err)
+		}
+		$result = string(b)
+	}
+%}
+
+%typemap(in) MyStruct
+%{
+  $1.str.assign($input.p, $input.n);
+%}
+
+%typemap(gotype) RetStruct "map[string]interface{}"
+
+%typemap(imtype) RetStruct "string"
+
+%typemap(out) RetStruct
+%{
+  $result = _swig_makegostring($1.str.data(), $1.str.length());
+%}
+
+%typemap(goout) RetStruct
+%{
+	if err := json.Unmarshal([]byte($1), &$result); err != nil {
+		panic(err)
+	}
+%}
+
+%inline
+%{
+
+RetStruct Same(MyStruct s)
+{
+  RetStruct r;
+  r.str = s.str;
+  return r;
+}
+
+%}