如何在mux.Vars中设置值（请求）

I want to set a value in mux.Vars() with MatcherFunc return true, then handlerFun can access to read. But panic assignment to entry in nil map when mux.Vars(request)["key"] = "value"

How can I set a value:

domainRouter := router.MatcherFunc(func(request *http.Request, match *mux.RouteMatch) bool {
    if isOk {
        mux.Vars(request)["key"] = "value"
        return true
    }
    return false
}).Subrouter()

This part of code is correct, the issue is in the place where you create mux.NewRouter(), it seems like your domainRouter is called before mux.NewRouter().