Goroutine launch puzzler

this doesn't

package main
import (
  . "fmt"
  . "net/http"
)

const ADDRESS = ":1024"
const SECURE_ADDRESS = ":1025"

func main() {
  message := "hello world"
  HandleFunc("/hello", func(w ResponseWriter, r *Request) {
    w.Header().Set("Content-Type", "text/plain")
    Fprintf(w, message)
  })

  Spawn(
	func() { ListenAndServe(ADDRESS, nil) },
    func() { ListenAndServeTLS(SECURE_ADDRESS, "cert.pem", "key.pem", nil) },
  )
}

func Spawn(f ...func()) {
  done := make(chan bool)

  for _, s := range f {
    go func() {
      s()
      done <- true
    }()
  }

  for l := len(f); l > 0; l-- {
    <- done
  }
}

this works

package main
import (
  . "fmt"
  . "net/http"
)

const ADDRESS = ":1024"
const SECURE_ADDRESS = ":1025"

func main() {
  message := "hello world"
  HandleFunc("/hello", func(w ResponseWriter, r *Request) {
    w.Header().Set("Content-Type", "text/plain")
    Fprintf(w, message)
  })

  Spawn(
	func() { ListenAndServe(ADDRESS, nil) },
    func() { ListenAndServeTLS(SECURE_ADDRESS, "cert.pem", "key.pem", nil) },
  )
}

func Spawn(http, https func()) {
  done := make(chan bool)

  go func() {
    http()
    done <- true
  }()

  go func() {
    https()
    done <- true
  }()

  <- done
  <- done
}

This took me a little while to figure out. The issue is that the function doesn't have a closure over the function s.

Try changing the body of the for loop in "This doesn't" to something like this.

  for _, s := range f {
    a := func(fun func()) {
      fun()
      done <- true
    }
    go a(s)
  }

Go doesn't capture external variables.

Here is a better explanation that I found https://code.google.com/p/go-wiki/wiki/CommonMistakes

Edit: Changed i back to _