jwt: add updateKeys method and call in constructor

Fixes #225.

middleware/jwt/jwt.go

@@ -57,37 +57,14 @@ func NewHook(cfg Config) middleware.Hook {
 		closing:    make(chan struct{}),
 	}
 
+	h.updateKeys()
 	go func() {
 		for {
 			select {
 			case <-h.closing:
 				return
 			case <-time.After(cfg.JWKUpdateInterval):
-				resp, err := http.Get(cfg.JWKSetURL)
+				h.updateKeys()
-				if err != nil {
-					log.Errorln("failed to fetch JWK Set: " + err.Error())
-					continue
-				}
-
-				parsedJWKs := map[string]gojwk.Key{}
-				err = json.NewDecoder(resp.Body).Decode(&parsedJWKs)
-				if err != nil {
-					resp.Body.Close()
-					log.Errorln("failed to decode JWK JSON: " + err.Error())
-					continue
-				}
-				resp.Body.Close()
-
-				keys := map[string]crypto.PublicKey{}
-				for kid, parsedJWK := range parsedJWKs {
-					publicKey, err := parsedJWK.DecodePublicKey()
-					if err != nil {
-						log.Errorln("failed to decode JWK into public key: " + err.Error())
-						continue
-					}
-					keys[kid] = publicKey
-				}
-				h.publicKeys = keys
 			}
 		}
 	}()
@@ -95,6 +72,34 @@ func NewHook(cfg Config) middleware.Hook {
 	return h
 }
 
+func (h *hook) updateKeys() {
+	resp, err := http.Get(h.cfg.JWKSetURL)
+	if err != nil {
+		log.Errorln("failed to fetch JWK Set: " + err.Error())
+		return
+	}
+
+	parsedJWKs := map[string]gojwk.Key{}
+	err = json.NewDecoder(resp.Body).Decode(&parsedJWKs)
+	if err != nil {
+		resp.Body.Close()
+		log.Errorln("failed to decode JWK JSON: " + err.Error())
+		return
+	}
+	resp.Body.Close()
+
+	keys := map[string]crypto.PublicKey{}
+	for kid, parsedJWK := range parsedJWKs {
+		publicKey, err := parsedJWK.DecodePublicKey()
+		if err != nil {
+			log.Errorln("failed to decode JWK into public key: " + err.Error())
+			return
+		}
+		keys[kid] = publicKey
+	}
+	h.publicKeys = keys
+}
+
 func (h *hook) Stop() <-chan error {
 	select {
 	case <-h.closing: