Copy metadata

metadata/metadata.go

@@ -12,6 +12,14 @@ type metaKey struct{}
 // from Transport headers.
 type Metadata map[string]string
 
+func Copy(md Metadata) Metadata {
+	cmd := make(Metadata)
+	for k, v := range md {
+		cmd[k] = v
+	}
+	return cmd
+}
+
 func FromContext(ctx context.Context) (Metadata, bool) {
 	md, ok := ctx.Value(metaKey{}).(Metadata)
 	return md, ok