cmd/go: tests that panic or exit are marked as passing when -json flag is used [1.14 backport] #37671
Description
@dmitshur requested issue #37555 to be considered for backport to the next 1.14 minor release.
This reproduces on tip as well. I'll change this issue to Go 1.15 milestone, and ask @gopherbot to please backport this to Go 1.14. Based on information so far, this looks like a serious bug that likely doesn't have a viable workaround.