Cleanup code

This changes variable names that were abbreviations, uses more constants
from the net/http package and improves the json decoding / encoding.

api/api.go

@@ -1,8 +1,11 @@
 package api
 
-import "github.com/gorilla/mux"
+import (
+	"github.com/gorilla/mux"
+	"net/http"
+)
 
-// NewRouter returns an HTTP handler (net.Handler) which can then
+// NewRouter returns an HTTP handler (http.Handler) which can then
 // be used by the net/http package to serve the api of our API.
 // We use gorilla/mux because it is more convenient than net/http,
 // e.g. when extracting path parameters.
@@ -11,7 +14,7 @@ func NewRouter() *mux.Router {
 	// this can later be restricted to a specific host with
 	// `router.Host(...)` and to HTTPS with `router.Schemes("https")`
 	v1 := router.PathPrefix("/api/v1").Subrouter()
-	v1.HandleFunc("/health", Health).Methods("GET")
+	v1.HandleFunc("/health", Health).Methods(http.MethodGet)
 
 	return v1
 }

api/health.go

@@ -6,14 +6,14 @@ import (
 	"net/http"
 )
 
-// Health sends the response that the API works. If it
-// it is able to do so, it is obviously correct.
+// Health tries to respond that the server is alive.
+// If it is not, the response won't reach the client.
 func Health(w http.ResponseWriter, r *http.Request) {
 	w.WriteHeader(http.StatusOK)
 	w.Header().Set("Content-Type", "application/json")
 	response, err := json.Marshal(Message{"I'm alive!"})
 	if err != nil {
-		log.Printf("Error formatting the health route: %v\n", err)
+		log.Printf("JSON marshal error in health route: %v\n", err)
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 	}
 	if _, err := w.Write(response); err != nil {

api/health_test.go

@@ -9,15 +9,15 @@ import (
 )
 
 func TestHealthRoute(t *testing.T) {
-	req, err := http.NewRequest("GET", "/health", nil)
+	request, err := http.NewRequest(http.MethodGet, "/health", nil)
 	if err != nil {
 		t.Fatal(err)
 	}
-	rec := httptest.NewRecorder()
-	http.HandlerFunc(Health).ServeHTTP(rec, req)
-	res := &Message{}
-	_ = json.NewDecoder(rec.Body).Decode(res)
+	recorder := httptest.NewRecorder()
+	http.HandlerFunc(Health).ServeHTTP(recorder, request)
+	result := Message{}
+	_ = json.Unmarshal(recorder.Body.Bytes(), &result)
 
-	assert.Equal(t, http.StatusOK, rec.Code)
-	assert.Equal(t, "I'm alive!", res.Msg)
+	assert.Equal(t, http.StatusOK, recorder.Code)
+	assert.Equal(t, "I'm alive!", result.Message)
 }

api/response_messages.go

@@ -1,5 +1,5 @@
 package api
 
 type Message struct {
-	Msg string `json:"msg"`
+	Message string `json:"msg"`
 }