type MyStruct struct {
    FirstName       [7]rune
    LastName        [7]rune
    Organization    [7]rune
}

func main () {
    // this is a line that needs to be mapped to MyStruct
    // its length is always 21 characters, 7 for each of the fields
    text := "John   Smith  Demo   "
    runes := []rune(text)
    str := reflect.New(MyStruct).Elem()
    for i := 0; i < str.NumField(); i++ {
        // reuse the rune array length so we know when each field from the text ends
        end := str.Field(i).Len()
        // reflect.Set: value of type []int32 is not assignable to type [7]int32
        str.Field(i).Set(reflect.ValueOf(runes[:end]))
        runes = runes[end:]
    }
}