Using local values in function definitions

The following program

package main
import (
  "fmt"
)
type TestFunc func()
func main() {
  fmt.Println()
  funcs := []TestFunc{}
  for i:=0; i<5; i++ {
    //i := i
    funcs = append(funcs, func() {fmt.Println(i)})
  }
  for _, f := range funcs {
    f()
  }
}

produces an output 5, 5, 5, 5, 5. After uncommenting the line, the program

  for i:=0; i<5; i++ {
    i := i
    funcs = append(funcs, func() {fmt.Println(i)})
  }
  for _, f := range funcs {
    f()
  }

produces an output 0, 1, 2, 3, 4.

Is there a better (or an idiomatic) way to pass the current value to a function declaration instead of using i := i?

That is the idiomatic way of doing it.

You also could pass it as an argument, if you were calling the function immediately.