Deques are great. I think there's two ways I'd consider designing this library differently:

1) The resizing seems worse to me than a linked-list of fixed-size ring buffers which use a sync.Pool. 2) (more out there) some of the time when I've implemented this sort of thing, it's been to allocate memory for unmarshaling. It might be nice to have a mechanism to store values and allocate pointers.