Changes

• Ensure that exponential backoff does not overflow giving unexpected - values backoff for retries higer than 37.
• Also add an exponential backoff with a max bound so it doesn't just go until ~290 years, useful for retry scenarios that should run "indefinitely" in the hopes a self healing service e.g a service in kubernetes comes back up.
• Suggestion to add a if a == 0 to exponentBase2 as its mathematically correct for any nonzero integers raised to the power of 0 to be 1 not 0 and adding a boundary to avoid overflowing int64 which durations uses.
• Another suggestion could be to do use math.Exp2

using math.Exp2 does add a bit of overhead but not a lot.

BenchmarkPowerCalculations/BitShift-16         	1000000000	         0.2438 ns/op	       0 B/op	       0 allocs/op
BenchmarkPowerCalculations/Pow-16              	19786604	        59.27 ns/op	       0 B/op	       0 allocs/op
BenchmarkPowerCalculations/Exp2-16             	559875931	         2.116 ns/op	       0 B/op	       0 allocs/op

Verification

Added unit tests