Imports of package backoff

PathSynopsis
github.com/golang/glogPackage glog implements logging analogous to the Google-internal C++ INFO/ERROR/V setup.
math/randPackage rand implements pseudo-random number generators suitable for tasks such as simulation, but it should not be used for security-sensitive work.
syncPackage sync provides basic synchronization primitives such as mutual exclusion locks.
timePackage time provides functionality for measuring and displaying time.