at least it works now

handler.go

@@ -147,7 +147,7 @@ func (t *Tmpauth) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error)
 
 			t.DebugLog(fmt.Sprintf("proxying request to mini server: %s", u.String()))
 
-			resp, err := t.miniClient.Do(req)
+			resp, err := t.miniClient(req)
 			if err != nil {
 				return http.StatusInternalServerError, err
 			}
@@ -282,7 +282,7 @@ func (t *Tmpauth) StartAuth(w http.ResponseWriter, r *http.Request) (int, error)
 		req.Header.Set(HostHeader, r.Host)
 		req.Header.Set("Content-Type", "application/jwt")
 
-		resp, err := t.miniClient.Do(req)
+		resp, err := t.miniClient(req)
 		if err != nil {
 			return http.StatusInternalServerError, fmt.Errorf("StartAuth on mini server: %w", err)
 		}
@@ -400,7 +400,7 @@ func (t *Tmpauth) Whomst() (map[string]json.RawMessage, error) {
 
 		req.Header.Set(ConfigIDHeader, t.miniConfigID)
 
-		resp, respErr = t.miniClient.Do(req)
+		resp, respErr = t.miniClient(req)
 	} else {
 		resp, respErr = t.HttpClient.Get("https://" + TmpAuthHost + "/whomst")
 	}

mini.go

@@ -34,21 +34,6 @@ type RemoteConfig struct {
 	Secret   []byte
 }
 
-// the registry and TransportWorkaround are used to work around a bug in yaegi.
-var transportRegistry = make(map[string]func(req *http.Request) (*http.Response, error))
-
-type TransportWorkaround struct {
-	configID string
-}
-
-func (t TransportWorkaround) RoundTrip(req *http.Request) (*http.Response, error) {
-	return transportRegistry[t.configID](req)
-}
-
-func DoTransportWorkaround(a interface{}) http.RoundTripper {
-	return a.(http.RoundTripper)
-}
-
 func NewMini(config MiniConfig, next CaddyHandleFunc) (*Tmpauth, error) {
 	var lastErr error
 	var remoteConfig RemoteConfig
@@ -138,14 +123,7 @@ func NewMini(config MiniConfig, next CaddyHandleFunc) (*Tmpauth, error) {
 		tmpauth: t,
 	}
 
-	transportRegistry[remoteConfig.ConfigID] = transport.RoundTrip
-
-	t.miniClient = &http.Client{
-		CheckRedirect: func(req *http.Request, via []*http.Request) error {
-			return http.ErrUseLastResponse
-		},
-		Transport: DoTransportWorkaround(TransportWorkaround{configID: remoteConfig.ConfigID}),
-	}
+	t.miniClient = transport.RoundTrip
 
 	return t, nil
 }

setup.go

@@ -55,7 +55,7 @@ type Tmpauth struct {
 	miniServerHost string
 	miniConfigID   string
 	miniConfigJSON []byte
-	miniClient     *http.Client
+	miniClient     func(req *http.Request) (*http.Response, error)
 
 	done     chan struct{}
 	doneOnce sync.Once

token.go

@@ -107,7 +107,7 @@ func (t *Tmpauth) ParseWrappedAuthJWT(tokenStr string) (*CachedToken, error) {
 		req.Header.Set(ConfigIDHeader, t.miniConfigID)
 		req.Header.Set("Content-Type", "application/jwt")
 
-		resp, err := t.miniClient.Do(req)
+		resp, err := t.miniClient(req)
 		if err != nil {
 			return nil, fmt.Errorf("ParseWrappedAuthJWT on mini server: %w", err)
 		}