go - Why is there a race condition in this program? -

I am looking at the Golg book, and I do not quite understand what is the problem in this program: / P>

  func main () {var wg sync.weaitgroup wg.Add (5) i: for = 0; I & lt; 5; I ++ {go func () {fmt.Println (i) // You are not looking for 'i' Wg.Done ()} ()} wg.Wait ()}   
 It prints  5, 5, 5, 5, 5  when I expect print  0, 1, 2, 3, 4  (not necessarily In this order).  
 The way I see it, when Gourdin is made inside the loop, its value is known  i  (for example, someone can log a  Printline (i)  at the beginning of the loop and see the expected value). So I hope Gortine is expected to capture the value of  i , when it is made and used later.  
 Obviously this is happening, but why?   
 
 
 Your task references  i  to external reference if you type  I , the value of whatever you get  i  is now the price of  i  To use, provide an argument:  
  func main () {var wg sync.WaitGroup wg. Add (5) for I: = 0; I & lt; 5; I ++ {go func (i int) {fmt.Println (i) wg.Done ()} (i)} wg.Wait ()}