all goroutines are asleep - deadlock!

program1

package main

import (
	"log"
)

func main() {
	done := make(chan struct{})
	go func() {
		log.Println("done")
	}()
	<-done //wait for background goroutine to finish
}

program2 run nc -l 8000 on another terminal

package main

import (
	"log"
	"net"
)

func main() {
	conn, err := net.Dial("tcp", "localhost:8000")
	if err != nil {
		log.Fatal(err)
	}
	conn.Close()
	done := make(chan struct{})
	go func() {
		log.Println("done")
	}()
	<-done //wait for background goroutine to finish
}

Both of those examples have a receive statement from a channel that no one ever sends to. Such a statement must block forever, meaning the goroutine that contains it can never run. If there are no goroutines that can run, Go terminates the program with a deadlock message.

However program2 wasn’t deadlocking. I couldn’t figure out why. Later, Tim clarified that

deadlock detection is disabled in certain situations, including when something in your program imports net.

That explained me why program2 wasn’t deadlocking.

• Go