jwt: add updateKeys method and call in constructor

Fixes #225.

middleware/jwt/jwt.go

@@ -57,16 +57,26 @@ 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()
+			}
+		}
+	}()
+
+	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())
-					continue
+		return
 	}
 
 	parsedJWKs := map[string]gojwk.Key{}
@@ -74,7 +84,7 @@ func NewHook(cfg Config) middleware.Hook {
 	if err != nil {
 		resp.Body.Close()
 		log.Errorln("failed to decode JWK JSON: " + err.Error())
-					continue
+		return
 	}
 	resp.Body.Close()
 
@@ -83,16 +93,11 @@ func NewHook(cfg Config) middleware.Hook {
 		publicKey, err := parsedJWK.DecodePublicKey()
 		if err != nil {
 			log.Errorln("failed to decode JWK into public key: " + err.Error())
-						continue
+			return
 		}
 		keys[kid] = publicKey
 	}
 	h.publicKeys = keys
-			}
-		}
-	}()
-
-	return h
 }
 
 func (h *hook) Stop() <-chan error {