What is the proper way to detect a dropped connection in Go? - http

Question

I am working with a Go HTTP server implementation that reads an upload from a mobile client. However, I'm experiencing problems where because of a long keep-alive, the server will hang reading the request buffer for quite a long time if the mobile client goes offline (as often happens).
What is the proper way to detect a dropped connection and close the input buffer?

Answer 1

Set a reasonable timeout on the server, for example:
srv := &http.Server{
Addr: ":443",
ReadTimeout: time.Minute * 2,
WriteTimeout: time.Minute * 2,
}
log.Fatal(srv.ListenAndServeTLS(certFile, keyFile))

Answer 2

Because I wanted to drop the connection only when writes stop (and quickly, so that I can record the data received so far and allow the client to resume), the ReadTimeout isn't the right solution for me.
I found the answer in this gist. You need to set a read on the connection itself.
package nettimeout
import (
"net"
"time"
)
// Listener wraps a net.Listener, and gives a place to store the timeout
// parameters. On Accept, it will wrap the net.Conn with our own Conn for us.
type Listener struct {
net.Listener
ReadTimeout time.Duration
WriteTimeout time.Duration
}
func (l *Listener) Accept() (net.Conn, error) {
c, err := l.Listener.Accept()
if err != nil {
return nil, err
}
tc := &Conn{
Conn: c,
ReadTimeout: l.ReadTimeout,
WriteTimeout: l.WriteTimeout,
}
return tc, nil
}
// Conn wraps a net.Conn, and sets a deadline for every read
// and write operation.
type Conn struct {
net.Conn
ReadTimeout time.Duration
WriteTimeout time.Duration
}
func (c *Conn) Read(b []byte) (int, error) {
err := c.Conn.SetReadDeadline(time.Now().Add(c.ReadTimeout))
if err != nil {
return 0, err
}
return c.Conn.Read(b)
}
func (c *Conn) Write(b []byte) (int, error) {
err := c.Conn.SetWriteDeadline(time.Now().Add(c.WriteTimeout))
if err != nil {
return 0, err
}
return c.Conn.Write(b)
}
func NewListener(addr string, readTimeout, writeTimeout time.Duration) (net.Listener, error) {
l, err := net.Listen("tcp", addr)
if err != nil {
return nil, err
}
tl := &Listener{
Listener: l,
ReadTimeout: readTimeout,
WriteTimeout: writeTimeout,
}
return tl, nil
}