fatal error: concurrent map writes in hyperloglog

fatal error: concurrent map writes

goroutine 1319496 [running]:
runtime.throw(0xee179f, 0x15)
    /usr/local/go/src/runtime/panic.go:605 +0x95 fp=0xc429110ab8 sp=0xc429110a98 pc=0x42d5f5
runtime.mapassign_fast32(0xdec5e0, 0xc42a2226c0, 0x26c6e40, 0x9b1b9024c9e69987)
    /usr/local/go/src/runtime/hashmap_fast.go:431 +0x3d2 fp=0xc429110b18 sp=0xc429110ab8 pc=0x40e1b2
github.com/coreos/etcdlabs/vendor/github.com/axiomhq/hyperloglog.set.add(...)
    /gopath/src/github.com/coreos/etcdlabs/vendor/github.com/axiomhq/hyperloglog/sparse.go:39
github.com/coreos/etcdlabs/vendor/github.com/axiomhq/hyperloglog.(*Sketch).Insert(0xc420223e30, 0xc42f4f80c0, 0x2f, 0x30)
    /gopath/src/github.com/coreos/etcdlabs/vendor/github.com/axiomhq/hyperloglog/hyperloglog.go:189 +0x98 fp=0xc429110b50 sp=0xc429110b18 pc=0xc6e398
github.com/coreos/etcdlabs/backend/web.withCache.func1(0x14354a0, 0xc4200fcd80, 0x1434120, 0xc42fd92ee0, 0xc42f3eb200, 0x0, 0x0)
    /gopath/src/github.com/coreos/etcdlabs/backend/web/handler.go:88 +0x12e fp=0xc429110c10 sp=0xc429110b50 pc=0xc7b1ce
github.com/coreos/etcdlabs/backend/web.ContextHandlerFunc.ServeHTTPContext(0xc428ae68e0, 0x14354a0, 0xc4200fcd80, 0x1434120, 0xc42fd92ee0, 0xc42f3eb200, 0xc420021900, 0x0)
    /gopath/src/github.com/coreos/etcdlabs/backend/web/context.go:34 +0x58 fp=0xc429110c58 sp=0xc429110c10 pc=0xc70e28
github.com/coreos/etcdlabs/backend/web.(*ContextAdapter).ServeHTTP(0xc428ae6900, 0x1434120, 0xc42fd92ee0, 0xc42f3eb200)
    /gopath/src/github.com/coreos/etcdlabs/backend/web/context.go:44 +0x73 fp=0xc429110cd8 sp=0xc429110c58 pc=0xc70ec3
net/http.(*ServeMux).ServeHTTP(0xc4290fe3f0, 0x1434120, 0xc42fd92ee0, 0xc42f3eb200)
    /usr/local/go/src/net/http/server.go:2254 +0x130 fp=0xc429110d18 sp=0xc429110cd8 pc=0x6810b0
net/http.serverHandler.ServeHTTP(0xc42029a0d0, 0x1434120, 0xc42fd92ee0, 0xc42f3eb200)
    /usr/local/go/src/net/http/server.go:2619 +0xb4 fp=0xc429110d48 sp=0xc429110d18 pc=0x6826e4
net/http.(*conn).serve(0xc42bc1f5e0, 0x14354a0, 0xc43081b700)
    /usr/local/go/src/net/http/server.go:1801 +0x71d fp=0xc429110fc8 sp=0xc429110d48 pc=0x67e8dd
runtime.goexit()
    /usr/local/go/src/runtime/asm_amd64.s:2337 +0x1 fp=0xc429110fd0 sp=0xc429110fc8 pc=0x45e471
created by net/http.(*Server).Serve
    /usr/local/go/src/net/http/server.go:2720 +0x288

goroutine 1 [select, 224 minutes]:
main.main()
    /gopath/src/github.com/coreos/etcdlabs/cmd/backend-web-server/main.go:47 +0x341
Full logs: panic.txt
etcd-io / etcdlabs

fatal error: concurrent map writes in hyperloglog #282
