broker: add SetPublishOption

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

broker/context.go

@@ -42,6 +42,16 @@ func SetSubscribeOption(k, v interface{}) SubscribeOption {
 	}
 }
 
+// SetPublishOption returns a function to setup a context with given value
+func SetPublishOption(k, v interface{}) PublishOption {
+	return func(o *PublishOptions) {
+		if o.Context == nil {
+			o.Context = context.Background()
+		}
+		o.Context = context.WithValue(o.Context, k, v)
+	}
+}
+
 // SetOption returns a function to setup a context with given value
 func SetOption(k, v interface{}) Option {
 	return func(o *Options) {