Unable to read from UNIX socket using net.Conn.Read - go

Question

I'm trying to do simple UNIX socket communication with a service using GO. For testing I've created a socket like so:
$ nc -vlU /tmp/sock
Bound on /tmp/sock
Listening on /tmp/sock
And in GO, I net.Dial and try to write something, then read. I see the written data in the nc console, so I know that is working. But the net.Conn.Read operation appears non-blocking and will return immediately with zero length. From everything I've read and the example I've seen, this operation should block.
buf := make([]byte, 0, 4096)
ctl, err := net.Dial("unix", "/tmp/sock")
for {
ctl.Write([]byte("test write\n"))
n, err := ctl.Read(buf)
fmt.Printf("Len:%v, Data:%v, err:%v", n, buf, err)
}
I see the connection come through and data written ...
Connection received on /tmp/sock
test write
test write
test write
test write
...
But the GO console loops without blocking, reporting a zero length and no error
Len:0, Data:[], err:<nil>
Len:0, Data:[], err:<nil>
Len:0, Data:[], err:<nil>
Len:0, Data:[], err:<nil>
...
And of course if I type anything into the nc console nothing interesting happens in the GO program output.
Any idea what I'm doing wrong?

Answer 1

short answer
buf := make([]byte, 0, 4096)
this code make a buffer with len=0!!!
do it like
buf := make([]byte, 4096)
example
this is some example i used, and they all works.
In practice, socket read and write should happen in two goroutines
package main
import (
"bufio"
"fmt"
"io"
"net"
"time"
)
func main() {
buf := make([]byte, 0, 4096)
fmt.Println(buf)
main03()
}
func main01() {
// nc -vlU /tmp/sock0120
ctl, err := net.Dial("unix", "/tmp/sock0120")
if err != nil {
fmt.Println(err)
return
}
reader := bufio.NewReader(ctl)
for {
time.Sleep(time.Second)
ctl.Write([]byte("test write\n"))
msg, err := reader.ReadString('\n')
fmt.Printf("Len:%v, Data:%v, err:%v\n", len(msg), msg, err)
}
}
func main02() {
// nc -vlU /tmp/sock0120
buf := make([]byte, 4)
ctl, err := net.Dial("unix", "/tmp/sock0120")
if err != nil {
fmt.Println(err)
return
}
reader := bufio.NewReader(ctl)
for {
time.Sleep(time.Second)
ctl.Write([]byte("test write\n"))
n, err := io.ReadFull(reader, buf)
fmt.Printf("Len:%v, Data:%v, err:%v\n", n, buf, err)
}
}
func main03() {
// nc -vlU /tmp/sock0120
buf := make([]byte, 4)
ctl, err := net.Dial("unix", "/tmp/sock0120")
if err != nil {
fmt.Println(err)
return
}
for {
time.Sleep(time.Second)
ctl.Write([]byte("test write\n"))
n, err := ctl.Read(buf)
fmt.Printf("Len:%v, Data:%v, err:%v\n", n, buf, err)
}
}