How to pass X-Auth-Token to headers

the token is saved by

.exec(http("GetToken")
...
.queryParamMap(Map("username" -> "admin", "password" -> "admin"))
.check(jsonPath("$.token").find.saveAs("auth")))

want to pass the token to another query, but looks like it does not go through

.exec(http("GetOnlineId")
    .get("/api/isOnline/id3")
    .headers(Map("X-Auth-Token" -> "${auth}"))
    .check(status.is(200)))

it returns 406 to me… not sure how to fix it