revalidate,

s-maxage=60, stale-while-revalidate dont working
must-revalidate - 开源搜索 - oschina
allow `stale-while-revalidate` (and `stale-if-error`?
web性能优化之:no-cache与must-revalidate深入探究
allow `stale-while-revalidate` (and `stale-if-error`?