coprocess: use metadata as map[string]string, enhance conversion

coprocess.go

@@ -136,13 +136,6 @@ func (c *CoProcessor) ObjectFromRequest(r *http.Request) *coprocess.Object {
 	if c.HookType != coprocess.HookType_Pre && c.HookType != coprocess.HookType_CustomKeyCheck {
 		if session := ctxGetSession(r); session != nil {
 			object.Session = ProtoSessionState(session)
-			// If the session contains metadata, add items to the object's metadata map:
-			if len(session.MetaData) > 0 {
-				object.Metadata = make(map[string]string)
-				for k, v := range session.MetaData {
-					object.Metadata[k] = v.(string)
-				}
-			}
 		}
 	}
 
@@ -278,7 +271,10 @@ func (m *CoProcessMiddleware) ProcessRequest(w http.ResponseWriter, r *http.Requ
 
 	coProcessor.ObjectPostProcess(returnObject, r)
 
-	token := returnObject.Metadata["token"]
+	var token string
+	if returnObject.Session != nil {
+		token = returnObject.Session.Metadata["token"]
+	}
 
 	// The CP middleware indicates this is a bad auth:
 	if returnObject.Request.ReturnOverrides.ResponseCode > 400 {
@@ -320,10 +316,6 @@ func (m *CoProcessMiddleware) ProcessRequest(w http.ResponseWriter, r *http.Requ
 
 		returnedSession := TykSessionState(returnObject.Session)
 
-		// If the returned object contains metadata, add them to the session:
-		for k, v := range returnObject.Metadata {
-			returnedSession.MetaData[k] = string(v)
-		}
 		if extractor == nil {
 			sessionLifetime := returnedSession.Lifetime(m.Spec.SessionLifetime)
 			// This API is not using the ID extractor, but we've got a session: