rewrite to using new method

middleware/headers.go

@@ -0,0 +1,12 @@
+package middleware
+
+import "net/http"
+
+func Headers(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+
+		w.Header().Set("Content-Type", "application/json")
+
+		next.ServeHTTP(w, r)
+	})
+}