net/http: ResponseWriter leaves connection open after WriteTimeout

[jbardin]

go1.3.1

run the following http server:


```
package main

import (
    "fmt"
    "net/http"
    "time"
)

func handler(w http.ResponseWriter, r *http.Request) {
    time.Sleep(2 * time.Second)
    msg := []byte("Hello world!\n")
    n, err := w.Write(msg)
    fmt.Printf("Wrote %d out of %d bytes\n", n, len(msg))
    fmt.Println("Error was:", err)
}
func main() {
    http.HandleFunc("/", handler)
    server := http.Server{
        Addr:         ":8123",
        ReadTimeout:  time.Second,
        WriteTimeout: time.Second,
    }
    server.ListenAndServe()
}
```

What happens:

The Write always succeeds in this handler, and the connection is left open hanging the
client. 


What should happen:

- Connection closed due to timeout
- Preferably return an error when writes fail (though this may not be feasible due to
internal buffering)

[jbardin]

Comment 1:

Sorry, pasted the incorrect Server: There should be no ReadTimeout in that snippet
    server := http.Server{
        Addr:         ":8123",
        WriteTimeout: time.Second,
    }

[ianlancetaylor]

Comment 2:

Labels changed: added repo-main, release-go1.4.

[jbardin]

Comment 3:

Seems to be related to keepalive. 
An HTTP1.1 connection hangs, but an HTTP1.0 connection is closed imediately. 
If you do run the first server code I posted with both timeouts, the client takes 3s to
return because the connection is left in keepalive, and the ReadTimeout is what shuts it
down.

[rsc]

Comment 4:

Brad, can you look at this?

Status changed to Accepted.

[griesemer]

Comment 5:

Owner changed to @bradfitz.

[bradfitz]

Comment 6:

Found it. There are dozens of writes that don't check the error return value. It's
almost always fine because they're buffered, but you never know where a buffer boundary
will be. Some Flushes weren't checking either.
Note to self: the easiest fix is something like https://golang.org/cl/149340044
which catches them all. Needs tests.

Status changed to Started.

[rsc]

Comment 7:

Brad, still working on this?

[bradfitz]

Comment 8:

Issue #8648 has been merged into this issue.

[gopherbot]

Comment 9:

CL https://golang.org/cl/149340044 mentions this issue.

[bradfitz]

Comment 10:

This issue was closed by revision 9d51cd0.

Status changed to Fixed.

[bradfitz]

Comment 11:

Issue #8648 has been merged into this issue.