Initial commit: Go DNS microservice boilerplate

internal/middleware/apikey.go

@@ -0,0 +1,30 @@
+package middleware
+
+import (
+	"encoding/json"
+	"net/http"
+)
+
+func APIKey(key string) func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if key == "" {
+				next.ServeHTTP(w, r)
+				return
+			}
+
+			provided := r.Header.Get("X-API-Key")
+			if provided != key {
+				w.Header().Set("Content-Type", "application/json")
+				w.WriteHeader(http.StatusUnauthorized)
+				json.NewEncoder(w).Encode(map[string]string{
+					"error": "invalid or missing API key",
+					"code":  "UNAUTHORIZED",
+				})
+				return
+			}
+
+			next.ServeHTTP(w, r)
+		})
+	}
+}