Golang接口{}参数如何判断传值或传指针

interface{} parameter

例如，我使用net/RPC混淆

界面：

// description: Call invokes the named function, waits for it to complete, and returns its error status. 
func (client *Client) Call(serviceMethod string, args interface{}, reply interface{}) error 

rpc call error:reading body gob: attempt to decode into a non-pointer

所以如何区分何时应该传递指针或传递接口的值。