Convert []string to []interface{}

1. Create a utility function, like this

func ToGenericArray(arr ...interface{}) []interface{} {
    return arr
}

2. And use it:

func yourfunc(arr []interface{})  {
....
}

yourfunc(ToGenericArray([...]string{"a", "b", "c"}))

3. IMPORTANT NOTICE: the following will not work

func yourfunc(arr []interface{})  {
....
}

arr:=[...]string{"a", "b", "c"}

yourfunc(ToGenericArray(arr))

now I know I'm wrong, []type is a whole type, can't be considered as []interface{}.

Yes, and that is because interface{} is its own type (and not an "alias" for any other type).
As I mention in "what is the meaning of interface{} in golang?" (if v is a interface{} variable):

Beginner gophers are led to believe that “v is of any type”, but that is wrong.
v is not of any type; it is of interface{} type.

The FAQ mentions

they do not have the same representation in memory.

It is necessary to copy the elements individually to the destination slice.
This example converts a slice of int to a slice of interface{}:

t := []int{1, 2, 3, 4}
s := make([]interface{}, len(t))
for i, v := range t {
    s[i] = v
}

---

Tom L propose this example (in the comments):

package main

import "fmt"

func main() {

    x := []string{"a", "b", "c", "d"}
    fmt.Printf("%T: %v\n", x, x)

    //converting a []string to a []interface{}
    y := make([]interface{}, len(x))
    for i, v := range x {
        y[i] = v
    }
    fmt.Printf("%T: %v\n", y, y)

    //converting a []interface{} to a []string
    z := make([]string, len(y))
    for i, v := range y {
        z[i] = fmt.Sprint(v)
    }
    fmt.Printf("%T: %v\n", z, z)

}