From b6ff0e73ec7b2c09760851dcee7ea3be74c4be6d Mon Sep 17 00:00:00 2001
From: Yimin Chen <yimin.chen@live.com>
Date: Fri, 4 Nov 2022 21:32:36 -0700
Subject: [PATCH] Use recursive

---
 server.go | 26 ++++++++++----------------
 1 file changed, 10 insertions(+), 16 deletions(-)

diff --git a/server.go b/server.go
index 49041bc9192..346f75dba4b 100644
--- a/server.go
+++ b/server.go
@@ -1150,22 +1150,16 @@ func chainUnaryServerInterceptors(s *Server) {
 
 func chainUnaryInterceptors(interceptors []UnaryServerInterceptor) UnaryServerInterceptor {
 	return func(ctx context.Context, req interface{}, info *UnaryServerInfo, handler UnaryHandler) (interface{}, error) {
-		// the struct ensures the variables are allocated together, rather than separately, since we
-		// know they should be garbage collected together. This saves 1 allocation and decreases
-		// time/call by about 10% on the microbenchmark.
-		var state struct {
-			i    int
-			next UnaryHandler
-		}
-		state.next = func(ctx context.Context, req interface{}) (interface{}, error) {
-			if state.i == len(interceptors)-1 {
-				return interceptors[state.i](ctx, req, info, handler)
-			}
-			state.i++
-			defer func() { state.i-- }()
-			return interceptors[state.i-1](ctx, req, info, state.next)
-		}
-		return state.next(ctx, req)
+		return interceptors[0](ctx, req, info, getChainUnaryHandler(interceptors, 0, info, handler))
+	}
+}
+
+func getChainUnaryHandler(interceptors []UnaryServerInterceptor, curr int, info *UnaryServerInfo, finalHandler UnaryHandler) UnaryHandler {
+	if curr == len(interceptors)-1 {
+		return finalHandler
+	}
+	return func(ctx context.Context, req interface{}) (interface{}, error) {
+		return interceptors[curr+1](ctx, req, info, getChainUnaryHandler(interceptors, curr+1, info, finalHandler))
 	}
 }