如何使用net / http打破大块？

I have an http server with an endpoint that returns lots of data streamed from a db. The response is chunked (< Transfer-Encoding: chunked). And if I run into an error, like the DB crashing, I can use a panic & curl will warn me of an issue:

curl: (18) transfer closed with outstanding read data remaining

I don't want a panic though - I just want a simple log message. And if I recover() I don't get the error in curl so there's no indication of something breaking.

Is there a way to break an chunked http response without a panic?

That error you see from curl is because the connection was immediately closed by the http server when it saw the panic. In order to force the connection closed without a panic, you will have to hijack it:

// inside the http handler
// func(w http.ResponseWriter, r *http.Request) {

// to abort an HTTP/1.1 response
if w, ok := w.(http.Hijacker); ok {
    c, _, err := w.Hijack()
    if err != nil {
        log.Println("cannot close connection:", err)
        return
    }
    c.Close()
    return
}

In Go 1.7, hijacking (as proposed in JimB's answer) is probably the best solution. Unfortunately, it only works in HTTP/1.1 — it will not do anything useful in HTTP/2.

Go 1.8 introduces a new value ErrAbortHandler, and the official way of interrupting an HTTP reply mid-stream is panic(http.ErrAbortHandler), which works for both HTTP/1.1 and HTTP.2. This is described in issue 17790.