go: runtime: memory corruption on darwin/amd64

#!watchflakes
post <- goos == "darwin" && goarch == "amd64" && (
	log ~ `fatal error: found pointer to free object` ||
	log ~ `fatal error: found bad pointer in Go heap` ||
	log ~ `fatal error: workbuf is not empty` ||
	log ~ `schedule: holding locks` ||
	log ~ `fatal error: bad summary data` ||
	log ~ `fatal: morestack on gsignal` ||
	(log ~ `panic: runtime error: invalid memory address or nil pointer dereference` && log ~ `^\s*runtime\.sigpanic.*\n\s+.*\n\s*runtime\.sweepone`) ||
	(log ~ `SIGSEGV: segmentation violation` && log ~ `^\s*runtime\.spanOfUnchecked\(`))

Issue created automatically to collect these failures.

Example (log):

— watchflakes