httpclient

var persons []Person
server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
	defer func() {
		_ = r.Body.Close()
	}()
	body, _ := ioutil.ReadAll(r.Body)

	switch r.Method {
	case GET:
		if data, err := json.Marshal(persons); err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			_, _ = w.Write(nil)
		} else {
			w.WriteHeader(http.StatusOK)
			_, _ = w.Write(data)
		}
	case PUT:
		var p Person
		err := json.Unmarshal(body, &p)
		if err != nil {
			w.WriteHeader(http.StatusNotAcceptable)
			_, _ = w.Write([]byte("body in request is not a person"))
			return
		}
		persons = append(persons, p)
		w.WriteHeader(http.StatusOK)
	case POST:
		var p Person
		err := json.Unmarshal(body, &p)
		if err != nil {
			w.WriteHeader(http.StatusNotAcceptable)
			_, _ = w.Write([]byte("body in request is not a person"))
			return
		}
		indexToReplace := -1
		for index, pp := range persons {
			if pp.Name == p.Name {
				indexToReplace = index
				break
			}
		}
		if indexToReplace > -1 {
			persons[indexToReplace] = p
			w.WriteHeader(http.StatusOK)
			return
		}
		w.WriteHeader(http.StatusNotFound)
		_, _ = w.Write([]byte("the person not found"))
	case DELETE:
		var p Person
		err := json.Unmarshal(body, &p)
		if err != nil {
			w.WriteHeader(http.StatusNotAcceptable)
			_, _ = w.Write([]byte("body in request is not a person"))
			return
		}
		var newPersons []Person
		for _, pp := range persons {
			if pp.Name != p.Name {
				newPersons = append(newPersons, pp)
			}
		}
		if len(persons)-1 == len(newPersons) {
			persons = newPersons
			w.WriteHeader(http.StatusOK)
		} else {
			w.WriteHeader(http.StatusNotFound)
			_, _ = w.Write([]byte("the person not found"))
			return
		}
	}
}))
defer server.Close()

dog := Pet{Name: "wangwang", Color: "black"}
tom := Person{Name: "Tom", Age: 27, Pet: dog}

cat := Pet{Name: "miumu", Color: "white"}
joe := Person{Name: "Joe", Age: 3, Pet: cat}

addPerson(server.URL+"/add", tom)
addPerson(server.URL+"/add", joe)
queryPersons(server.URL + "/persons")
modifyPersonAge(server.URL+"/modify", joe, 5)
removePerson(server.URL+"/remove", tom)
queryPersons(server.URL + "/persons")

Output:

quiried persons: [{27 Tom {wangwang black}} {3 Joe {miumu white}}]
quiried persons: [{5 Joe {miumu white}}]