golang：客户端tls.Conn关闭钩子

Question

I am interacting with an http client API which accepts a *tls.Conn. I cannot change the API. I want some code to be executed when the connection is closed, but I don't see a way to do this. If I create a struct which embeds a *tls.Conn and I "override" Close(), the API won't accept the struct because go only follows the sub-type is-a relationship with interfaces - tls.Conn is not an interface.

Is there any way to get around this - is there some standard hook I can use to be notified when the client connection is closed?

Answer 1

If you're using tls.Client to construct the *tls.Conn then you can wrap the first argument to achieve your goal.

type CloseListener struct {
    net.Conn // embed the original conn
}

func (c *CloseListener) Close() error {
    err := c.Conn.Close()
    // ... do your stuff ...
    return err
}

conn := tls.Client(&CloseListener{c}, &tls.Config{ /* ... */ }) 

If you look at how tls.Conn's Close is implemented you'll see that it should call your Close implementation unless there was some error.