add m3o services (#2301)

* add m3o services

* update readme

services/helloworld/helloworld.go

@@ -0,0 +1,47 @@
+package helloworld
+
+import (
+	"github.com/m3o/m3o-go/client"
+)
+
+func NewHelloworldService(token string) *HelloworldService {
+	return &HelloworldService{
+		client: client.NewClient(&client.Options{
+			Token: token,
+		}),
+	}
+}
+
+type HelloworldService struct {
+	client *client.Client
+}
+
+// Call returns a personalised "Hello $name" response
+func (t *HelloworldService) Call(request *CallRequest) (*CallResponse, error) {
+	rsp := &CallResponse{}
+	return rsp, t.client.Call("helloworld", "Call", request, rsp)
+}
+
+// Stream returns a stream of "Hello $name" responses
+func (t *HelloworldService) Stream(request *StreamRequest) (*StreamResponse, error) {
+	rsp := &StreamResponse{}
+	return rsp, t.client.Call("helloworld", "Stream", request, rsp)
+}
+
+type CallRequest struct {
+	Name string `json:"name"`
+}
+
+type CallResponse struct {
+	Message string `json:"message"`
+}
+
+type StreamRequest struct {
+	// the number of messages to send back
+	Messages int64  `json:"messages,string"`
+	Name     string `json:"name"`
+}
+
+type StreamResponse struct {
+	Message string `json:"message"`
+}