feat(http): http client support service discovery in Do (#1563)

transport/http/client.go

@@ -232,27 +232,7 @@ func (client *Client) Invoke(ctx context.Context, method, path string, args inte
 
 func (client *Client) invoke(ctx context.Context, req *http.Request, args interface{}, reply interface{}, c callInfo, opts ...CallOption) error {
 	h := func(ctx context.Context, in interface{}) (interface{}, error) {
-		var done func(context.Context, selector.DoneInfo)
-		if client.r != nil {
-			var (
-				err  error
-				node selector.Node
-			)
-			if node, done, err = client.opts.selector.Select(ctx); err != nil {
-				return nil, errors.ServiceUnavailable("NODE_NOT_FOUND", err.Error())
-			}
-			if client.insecure {
-				req.URL.Scheme = "http"
-			} else {
-				req.URL.Scheme = "https"
-			}
-			req.URL.Host = node.Address()
-			req.Host = node.Address()
-		}
 		res, err := client.do(ctx, req, c)
-		if done != nil {
-			done(ctx, selector.DoneInfo{Err: err})
-		}
 		if res != nil {
 			cs := csAttempt{res: res}
 			for _, o := range opts {
@@ -284,16 +264,39 @@ func (client *Client) Do(req *http.Request, opts ...CallOption) (*http.Response,
 			return nil, err
 		}
 	}
-	return client.do(req.Context(), req, c)
+	ctx := req.Context()
+
+	return client.do(ctx, req, c)
 }
 
 func (client *Client) do(ctx context.Context, req *http.Request, c callInfo) (*http.Response, error) {
+	var done func(context.Context, selector.DoneInfo)
+	if client.r != nil {
+		var (
+			err  error
+			node selector.Node
+		)
+		if node, done, err = client.opts.selector.Select(ctx); err != nil {
+			return nil, errors.ServiceUnavailable("NODE_NOT_FOUND", err.Error())
+		}
+		if client.insecure {
+			req.URL.Scheme = "http"
+		} else {
+			req.URL.Scheme = "https"
+		}
+		req.URL.Host = node.Address()
+		req.Host = node.Address()
+	}
 	resp, err := client.cc.Do(req)
+	if err == nil {
+		err = client.opts.errorDecoder(ctx, resp)
+	}
+
 	if err != nil {
 		return nil, err
 	}
-	if err := client.opts.errorDecoder(ctx, resp); err != nil {
-		return nil, err
+	if done != nil {
+		done(ctx, selector.DoneInfo{Err: err})
 	}
 	return resp, nil
 }