refactor(serverHandler): use constants defined in http package instead of literals

Author: marjune163

src/serverHandler/cors.go

@@ -12,12 +12,20 @@ func (h *handler) cors(w http.ResponseWriter, r *http.Request) {
 	header.Set("Access-Control-Allow-Origin", "*")
 	header.Set("Access-Control-Allow-Credentials", "true")
 
-	if r.Method != "OPTIONS" {
+	if r.Method != http.MethodOptions {
 		return
 	}
 
 	// Access-Control-Allow-Methods
-	acAllowMethods := []string{"GET", "HEAD", "POST", "PUT", "DELETE", "OPTIONS", "TRACE"}
+	acAllowMethods := []string{
+		http.MethodGet,
+		http.MethodHead,
+		http.MethodPost,
+		http.MethodPut,
+		http.MethodDelete,
+		http.MethodOptions,
+		http.MethodTrace,
+	}
 	acReqMethods := r.Header["Access-Control-Request-Method"]
 	if len(acReqMethods) > 0 {
 		acReqMethod := acReqMethods[0]

src/serverHandler/main.go

@@ -81,7 +81,7 @@ func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		h.cors(w, r)
 	}
 
-	if data.CanUpload && r.Method == "POST" {
+	if data.CanUpload && r.Method == http.MethodPost {
 		h.saveUploadFiles(data.handlerReqPath, r)
 		http.Redirect(w, r, r.RequestURI, http.StatusFound)
 		return

src/serverHandler/util.go

@@ -1,5 +1,10 @@
 package serverHandler
 
+import "net/http"
+
 func needResponseBody(method string) bool {
-	return method != "HEAD" && method != "OPTIONS" && method != "CONNECT" && method != "TRACE"
+	return method != http.MethodHead &&
+		method != http.MethodOptions &&
+		method != http.MethodConnect &&
+		method != http.MethodTrace
 }