From 4fa909a3c78bed66da7a22a79851896c69ac3e43 Mon Sep 17 00:00:00 2001
From: Asim <asim@chuhnk.me>
Date: Thu, 26 Nov 2015 20:35:50 +0000
Subject: [PATCH] don't just overwrite the context metadata, append if already
 exists

---
 context/context.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/context/context.go b/context/context.go
index 8906eb00..b7c8ab93 100644
--- a/context/context.go
+++ b/context/context.go
@@ -18,5 +18,12 @@ func GetMetadata(ctx context.Context) (Metadata, bool) {
 }
 
 func WithMetadata(ctx context.Context, md Metadata) context.Context {
+	if emd, ok := ctx.Value(mdKey).(Metadata); ok {
+		for k, v := range emd {
+			if _, ok := md[k]; !ok {
+				md[k] = v
+			}
+		}
+	}
 	return context.WithValue(ctx, mdKey, md)
 }