Goroutine is blocked in execution [duplicate] - go

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Closed 26 days ago.
I try to work on a piece of code with goroutine to scan open port on a subnet.
Here is the code :
package main
import (
"fmt"
"log"
"net"
"time"
)
func is_445_open(ip string, ch chan string){
connexion, err := net.DialTimeout("tcp", ip + ":445", 3*time.Second )
if err != nil {
return
}
defer connexion.Close()
ch <- ip
}
func ip_suivante(ip net.IP) {
for j := len(ip) - 1; j >= 0; j-- {
ip[j]++
if ip[j] > 0 {
break
}
}
}
func main() {
ch := make(chan string)
ipv4Addr, ipv4Net, err := net.ParseCIDR("200.31.0.0/24")
if err != nil {
log.Fatal(err)
}
for ipv4Addr := ipv4Addr.Mask(ipv4Net.Mask); ipv4Net.Contains(ipv4Addr); ip_suivante(ipv4Addr) {
//fmt.Println(ipv4Addr.String())
go is_445_open(ipv4Addr.String(), ch)
}
for v := range ch{
fmt.Println(v)
}
fmt.Println("Done")
}
I use ParseCIDR to loop over every IP of the network range then i connect to the port 445 to test if it is open.
To speed up the process, i want to use goroutine and write the ip where 445 is open to a channel.
Then loop over it to print them on the console.
When i use the loop to print every IP on my console the program never end.
It print the ip correctly but never the "done" at the end.
I have tried to close the channel before looping but when i do, no more data is printed and the program only show "done".
Do you have any tips ?
EDIT :
Finally figured out. You MUST put the code which manage the waitgroup and the channel closing into another goroutine to make it work.
Cannot undestand why.
But here is the code modified accordingly :
package main
import (
"fmt"
"log"
"net"
"time"
"sync"
)
func is_445_open(ip string, ch chan string, wg *sync.WaitGroup){
connexion, err := net.DialTimeout("tcp", ip + ":445", 3*time.Second )
if err != nil {
wg.Done()
return
}
defer connexion.Close()
ch <- ip
wg.Done()
}
func ip_suivante(ip net.IP) {
for j := len(ip) - 1; j >= 0; j-- {
ip[j]++
if ip[j] > 0 {
break
}
}
}
func main() {
wg := &sync.WaitGroup{}
ch := make(chan string)
ipv4Addr, ipv4Net, err := net.ParseCIDR("192.168.1.0/24")
if err != nil {
log.Fatal(err)
}
for ipv4Addr := ipv4Addr.Mask(ipv4Net.Mask); ipv4Net.Contains(ipv4Addr); ip_suivante(ipv4Addr) {
//fmt.Println(ipv4Addr.String())
wg.Add(1)
go is_445_open(ipv4Addr.String(), ch, wg)
}
go func(cha chan string, wg *sync.WaitGroup){
wg.Wait()
close(cha)
}(ch,wg)
for v := range ch{
fmt.Println(v)
}
fmt.Println("Done")
}