pass two or more variables to expression,it doesn't work

[lx217197]

for k := range symbolTable {
s += k
}
symbols_rx = regexp.MustCompile(fmt.Sprintf("(%s)", s))
func Tokenis (expr string) []string {
if symbols_rx != nil {
spaced = symbols_rx.ReplaceAllString(spaced, " ${1} ")//it doesn't work
}
}