Helper for limiting a test's duration?

I've run across a few cases recently where I've wanted to set a deadline on a test running. Generally when doing potentially complicated things that could deadlock, and as mistake could accidentally leave the test hanging.

Would you be interesting in accepting a new function/package for this functionality?

There's some related disucssion in https://github.com/golang/go/issues/10529 where it was deemed not suitable for core.