Called inject.InterfaceOf with a value that is not a pointer to an interface. (*MyInterface)(nil)

[darcys22]

Have been trying to set up a JSON Post Request using the Macaron Example

  type ContactForm struct {
    Name string `json:"name" binding:"Required"`
  }
  r.Post("/api/journals", binding.Bind(ContactForm{}), func(contact ContactForm) string {
    return fmt.Sprintf("Name: %s", contact.Name)
  })

However calling this with the following JSON request from within jquery:

      $.ajax({
          type: 'POST',
          url: '/api/journals',
          data: '{"name":"hello"}',
          success: function(data) { alert('data: ' + data); },
          contentType: "application/json",
          dataType: 'json'
      });

returns the following error when the request is sent:

*Called inject.InterfaceOf with a value that is not a pointer to an interface. (MyInterface)(nil)

with the following stack trace:

/home/sean/go/pkg/mod/github.com/go-macaron/inject@v0.0.0-20160627170012-d8a0b8677191/inject.go:113 (0x792c6d)
	InterfaceOf: panic("Called inject.InterfaceOf with a value that is not a pointer to an interface. (*MyInterface)(nil)")
/home/sean/go/pkg/mod/github.com/go-macaron/inject@v0.0.0-20160627170012-d8a0b8677191/inject.go:222 (0x793a7e)
	(*injector).MapTo: i.values[InterfaceOf(ifacePtr)] = reflect.ValueOf(val)
/home/sean/go/pkg/mod/github.com/go-macaron/binding@v1.1.0/binding.go:752 (0x8258c4)
	validateAndMap: ctx.MapTo(obj.Elem().Interface(), ifacePtr[0])
/home/sean/go/pkg/mod/github.com/go-macaron/binding@v1.1.0/binding.go:210 (0x826edb)
	Json.func1: validateAndMap(jsonStruct, ctx, errors, ifacePtr...)
/usr/local/go/src/reflect/value.go:475 (0x49af66)
	Value.call: call(frametype, fn, args, uint32(frametype.size), uint32(retOffset))
/usr/local/go/src/reflect/value.go:336 (0x49a458)
	Value.Call: return v.call("Call", in)
/home/sean/go/pkg/mod/github.com/go-macaron/inject@v0.0.0-20160627170012-d8a0b8677191/inject.go:177 (0x793379)
	(*injector).callInvoke: return reflect.ValueOf(f).Call(in), nil
/home/sean/go/pkg/mod/github.com/go-macaron/inject@v0.0.0-20160627170012-d8a0b8677191/inject.go:137 (0x792d4a)
	(*injector).Invoke: return inj.callInvoke(f, t, t.NumIn())
/home/sean/go/pkg/mod/github.com/go-macaron/binding@v1.1.0/binding.go:45 (0x81e5be)
	bind: ctx.Invoke(Json(obj, ifacePtr...))
/home/sean/go/pkg/mod/github.com/go-macaron/binding@v1.1.0/binding.go:104 (0x8260c5)
	Bind.func1: bind(ctx, obj, ifacePtr...)
/home/sean/go/pkg/mod/gopkg.in/macaron.v1@v1.3.5/context.go:79 (0x7c5a72)
	ContextInvoker.Invoke: invoke(params[0].(*Context))
/home/sean/go/pkg/mod/github.com/go-macaron/inject@v0.0.0-20160627170012-d8a0b8677191/inject.go:157 (0x793094)
	(*injector).fastInvoke: return f.Invoke(in)
/home/sean/go/pkg/mod/github.com/go-macaron/inject@v0.0.0-20160627170012-d8a0b8677191/inject.go:135 (0x792e39)
	(*injector).Invoke: return inj.fastInvoke(v, t, t.NumIn())
/home/sean/go/pkg/mod/gopkg.in/macaron.v1@v1.3.5/context.go:121 (0x7c5bfc)
	(*Context).run: vals, err := c.Invoke(c.handler())
/home/sean/go/pkg/mod/gopkg.in/macaron.v1@v1.3.5/context.go:112 (0x7d6da5)
	(*Context).Next: c.run()
/home/sean/go/pkg/mod/gopkg.in/macaron.v1@v1.3.5/recovery.go:161 (0x7d6d98)
	Recovery.func1: c.Next()
/home/sean/go/pkg/mod/gopkg.in/macaron.v1@v1.3.5/logger.go:40 (0x7c97b7)
	LoggerInvoker.Invoke: invoke(params[0].(*Context), params[1].(*log.Logger))
/home/sean/go/pkg/mod/github.com/go-macaron/inject@v0.0.0-20160627170012-d8a0b8677191/inject.go:157 (0x793094)
	(*injector).fastInvoke: return f.Invoke(in)
/home/sean/go/pkg/mod/github.com/go-macaron/inject@v0.0.0-20160627170012-d8a0b8677191/inject.go:135 (0x792e39)
	(*injector).Invoke: return inj.fastInvoke(v, t, t.NumIn())
/home/sean/go/pkg/mod/gopkg.in/macaron.v1@v1.3.5/context.go:121 (0x7c5bfc)
	(*Context).run: vals, err := c.Invoke(c.handler())
/home/sean/go/pkg/mod/gopkg.in/macaron.v1@v1.3.5/router.go:187 (0x7d7ff0)
	(*Router).Handle.func1: c.run()
/home/sean/go/pkg/mod/gopkg.in/macaron.v1@v1.3.5/router.go:303 (0x7d2125)
	(*Router).ServeHTTP: h(rw, req, p)
/home/sean/go/pkg/mod/gopkg.in/macaron.v1@v1.3.5/macaron.go:220 (0x7cab0d)
	(*Macaron).ServeHTTP: m.Router.ServeHTTP(rw, req)
/usr/local/go/src/net/http/server.go:2843 (0x767bc2)
	serverHandler.ServeHTTP: handler.ServeHTTP(rw, req)
/usr/local/go/src/net/http/server.go:1925 (0x7633cc)
	(*conn).serve: serverHandler{c.server}.ServeHTTP(w, w.req)
/usr/local/go/src/runtime/asm_amd64.s:1374 (0x470480)
	goexit: BYTE	$0x90	// NOP