When you answer using io.Copy, who should be responsible for the error?

Question

Suppose that the server needs to respond to some data with the client, and the data comes from a file on the local disk. Then we write:

n, err := io.Copy(w, f)  // w is the ResponseWriter and f is the *os.File

I think that io.Copy()he writes the header first and then copies the data from fto w.

If errnot nil(say unexpected EOF), the client will still receive a 200 status code, although the response body contains something wrong.

The local disk may be damaged, or the client network may be broken. How can we determine if a errserver or client is calling ?

Answer 1

io.Copy Write io.Writer. http.ResponseWriter Write :

// Write writes the data to the connection as part of an HTTP reply.
// If WriteHeader has not yet been called, Write calls WriteHeader(http.StatusOK)
// before writing the data.  If the Header does not contain a
// Content-Type line, Write adds a Content-Type set to the result of passing
// the initial 512 bytes of written data to DetectContentType.
Write([]byte) (int, error)

, WriteHeader:

// WriteHeader sends an HTTP response header with status code.
// If WriteHeader is not called explicitly, the first call to Write
// will trigger an implicit WriteHeader(http.StatusOK).
// Thus explicit calls to WriteHeader are mainly used to
// send error codes.
WriteHeader(int)

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Answer 2

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