range over interface{} which stores a slice

Well I used reflect.ValueOf and then if it is a slice you can call Len() and Index() on the value to get the len of the slice and element at an index. I don't think you will be able to use the range operate to do this.

package main

import "fmt"
import "reflect"

func main() {
    data := []string{"one","two","three"}
    test(data)
    moredata := []int{1,2,3}
    test(moredata)
} 

func test(t interface{}) {
    switch reflect.TypeOf(t).Kind() {
    case reflect.Slice:
        s := reflect.ValueOf(t)

        for i := 0; i < s.Len(); i++ {
            fmt.Println(s.Index(i))
        }
    }
}

Go Playground Example: http://play.golang.org/p/gQhCTiwPAq

You don't need to use reflection if you know which types to expect. You can use a type switch, like this:

package main

import "fmt"

func main() {
    loop([]string{"one", "two", "three"})
    loop([]int{1, 2, 3})
}

func loop(t interface{}) {
    switch t := t.(type) {
    case []string:
        for _, value := range t {
            fmt.Println(value)
        }
    case []int:
        for _, value := range t {
            fmt.Println(value)
        }
    }
}

Check out the code on the playground.

Expanding on the answer provided by masebase, you could generalize the iteration on an interface{} slice with a function like this:

func forEachValue(ifaceSlice interface{}, f func(i int, val interface{})) {
    v := reflect.ValueOf(ifaceSlice)
    if v.Kind() == reflect.Ptr {
        v = v.Elem()
    }
    if v.Kind() != reflect.Slice {
        panic(fmt.Errorf("forEachValue: expected slice type, found %q", v.Kind().String()))
    }

    for i := 0; i < v.Len(); i++ {
        val := v.Index(i).Interface()
        f(i, val)
    }
}

Then, you use it like this:

func main() {
    data := []string{"one","two","three"}
    test(data)
    moredata := []int{1,2,3}
    test(data)
}

func test(sliceIface interface{}) {
    forEachValue(sliceIface, func(i int, value interface{}) {
      fmt.Println(value)
    }
}