context.SendFile supports resume (by range). https://github.com/kataras/iris/issues/359#issuecomment-240471538

plugin.go

@@ -248,7 +248,8 @@ func (p *pluginContainer) Add(plugins ...Plugin) error {
 		}
 		// Activate the plugin, if no error then add it to the plugins
 		if pluginObj, ok := plugin.(pluginActivate); ok {
-			tempPluginContainer := *p
+
+			tempPluginContainer := *p // contains the mutex but we' re safe here.
 			err := pluginObj.Activate(&tempPluginContainer)
 			if err != nil {
 				return errPluginActivate.Format(pName, err.Error())