golang: net.Conn: check conn status - go

Question

I encountered a strange behavior of the conn.Read:
let's presume that I have a couple of functions for testing net.Conn:
package example
import (
"io"
"log"
"net"
"os"
"time"
)
func CheckConn(conn net.Conn) (net.Conn, error) {
conn.SetReadDeadline(time.Now())
var one = []byte{}
_, err := conn.Read(one)
if err != nil {
log.Println("Net err: ", err)
}
if err == io.EOF {
return conn, err
}
var zero time.Time
conn.SetReadDeadline(zero)
return conn, nil
}
func CheckConnWithTimeout(conn net.Conn) (net.Conn, error) {
ch := make(chan bool, 1)
defer func() {
ch <- true
}()
go func() {
select {
case <-ch:
case <-time.After(1 * time.Second):
log.Println("It works too long")
os.Exit(1)
}
}()
return CheckConn(conn)
}
And I want to implement tests for it, lets start with this one:
package example
import (
"io"
"net"
"testing"
)
func TestClosedConn(t *testing.T) {
server, client := net.Pipe()
client.Close()
defer server.Close()
_, err := CheckConn(server)
if err != io.EOF {
t.Errorf("Not equal:\nExpected: %v\nactual: %v", io.EOF, err)
}
}
this works pretty well, we will receive io.EOF from CheckConn function, lets add one more test:
func TestClosedConnAfterWrite(t *testing.T) {
server, client := net.Pipe()
go func() {
client.Write([]byte{0xb})
}()
client.Close()
defer server.Close()
_, err := CheckConn(server)
err = nil
if err != io.EOF {
t.Errorf("Not equal:\nExpected: %v\nactual: %v", io.EOF, err)
}
}
looks like the first test, but we wrote to the client before(?) it was closed.
And this will not pass!
conn.Read will return &errors.errorString{s:"EOF"}, instead of io.EOF, so CheckConn will return error == nil,
It looks so weird!
But let's continue the tests, now I want to check unclosed connections:
func TestActiveConn(t *testing.T) {
server, client := net.Pipe()
defer client.Close()
defer server.Close()
_, err := CheckConnWithTimeout(server)
if err != nil {
t.Errorf("Not equal:\nExpected: %v\nactual: %v", nil, err)
}
}
I think you noticed that I use the function with a timeout just because SetReadDeadline will not work in this case(I have no idea why!)
So what is going wrong in last two test cases? Is there a normal way to test the connection? Why SetReadDeadline is not working in this case?