Cmd does not allow Wait to be called multiple times

[oneirocosm]

In the function definition of Wait for the Cmd struct, the finished boolean prevents Wait from being called more than once

if c.finished {
	return errors.New("Wait was already called")
}
c.finished = true

state, err := c.Process.Wait()

This behavior is different from exec.Cmd where Wait can be called multiple times. Allowing this makes certain concurrent tasks easier to synchronize.