Currently it crashes as follows:
fatal error: unknown pc
...
goroutine 71698 [runnable]:
runtime.racegoend()
        src/pkg/runtime/race.c:171
runtime.goexit()
        src/pkg/runtime/proc.c:1276 +0x9
created by runtime_test.testConcurrentReadsAfterGrowth
        src/pkg/runtime/map_test.go:264 +0x332

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/10674047