v clock duration is a timeout of duration, as measured by clock. Internally, this is just the tuple (clock, duration).

seconds clock duration is a timeout of duration seconds, as measured by clock.

none is an infinite timeout.

run t fn runs fn () but cancels it if it takes longer than allowed by timeout t.

run_exn t fn runs fn () but cancels it if it takes longer than allowed by timeout t, raising exception Timeout.

pp formats a timeout as a duration (e.g. "5s"). This is intended for use in error messages and logging and is rounded.