Panic not recovered within With

[jirenius]

Issue

When there is a panic within a With callback, the service will currently crash. This means using RequireValue, which panics if the Get handler returns an error, will be very dangerous within a With callback.

Example

s.With("library.book.1337", func(r res.Resource) {
    // Since RequireValue will panic if the Get handler
    // returns a NotFound error, the entire service will crash.
    book := r.RequireValue.(*Book)
})

Solution

Any panic that happens within the With callback should be recovered and logged as an error.

Since it the callback is (most likely) running on a different goroutine than the caller of With, it will not be possible to return any recovered panic as an error on the With call.