go - Wrapping a function call into a closure when using goroutines -

this question has answer here:

• why golang handle closures differently in goroutines? 2 answers

wrapping function call closure leads unexpected behaviour when using goroutines.

consider following example:

package main  import (     "log"     "sync"     "time" )  var workernum = 5 var wg sync.waitgroup  func block() {     dur := 300 * time.millisecond     //time.sleep()     select {     case <- time.after(dur): {}     } }  func startworker(worker int) {     i:=0; < 3; i++{         log.printf("worker %d woke up! \n", worker)         block()     }     wg.done() }  func main() {     i:=0; < workernum; i++ {         //go func() { startworker(i) }()         go startworker(i)     }      wg.add(workernum)     wg.wait() } 

test here: http://play.golang.org/p/nmlntkbwvf

one can see wrapping startworker(i) func() { startworker(i) }() results in calling 5-th worker.

it looks there wrong in way how closures capture variables outer scope. why happening? closures use pass-by-reference way passing outer variables instead of pass-by-value?

that's how closures in languages work, if want way, have isolate variable.

go func(i int) { startworker(i) }(i)