git diff gotrack.go 
diff --git a/http2/gotrack.go b/http2/gotrack.go
index 9933c9f..57196da 100644
--- a/http2/gotrack.go
+++ b/http2/gotrack.go
@@ -11,13 +11,12 @@ import (
    "bytes"
    "errors"
    "fmt"
-   "os"
    "runtime"
    "strconv"
    "sync"
 )

-var DebugGoroutines = os.Getenv("DEBUG_HTTP2_GOROUTINES") == "1"
+var DebugGoroutines = false

 type goroutineLock uint64

@@ -49,6 +48,8 @@ func (g goroutineLock) checkNotOn() {
 var goroutineSpace = []byte("goroutine ")

 func curGoroutineID() uint64 {
+   panic("how can we possibly be getting here?")
+
    bp := littleBuf.Get().(*[]byte)
    defer littleBuf.Put(bp)
    b := *bp

$ go test -c && ./http2.test -test.cpuprofile=prof -test.bench=BenchmarkServerPosts -test.run=XXX
BenchmarkServerPosts-4  --- FAIL: BenchmarkServerPosts-4
    http2_test.go:64: 2015/12/19 16:38:31 http: panic serving 127.0.0.1:54702: how can we possibly be getting here?
        goroutine 9 [running]:
        net/http.(*conn).serve.func1(0xc820ad6000)
            /Users/jra/go/src/net/http/server.go:1380 +0xc1
        golang.org/x/net/http2.curGoroutineID(0x0)
            /Users/jra/src/golang.org/x/net/http2/gotrack.go:51 +0x6e
        golang.org/x/net/http2.newGoroutineLock(0x38c620)
            /Users/jra/src/golang.org/x/net/http2/gotrack.go:27 +0x2f
        golang.org/x/net/http2.(*Server).handleConn(0xc8200e2660, 0xc82007a180, 0x949e90, 0xc820ad4000, 0xb26d80, 0xc8203c4080)
            /Users/jra/src/golang.org/x/net/http2/server.go:222 +0x23a