Modular Exponentiation in Golang

• Assume all arguments are positive.
• ModExpGoBigInteger calculates modular exponentiation using math/big package.
• ModExpGoBigIntegerExp calculates modular exponentiation using native Exp method from math/big package.
• ModExp calculates modular exponentiation in O(exponent).
• ModExpWithSquaring calculates modular exponentiation with exponentiation by squaring, O(log exponent).

# run tests
go test .

# benchmark
go test -bench .

Tested under Golang 1.9.2, 2.8 GHz Intel Core i7, macOS 10.13, calculating 81792 ^ 73363 mod 233.

goos: darwin
goarch: amd64
BenchmarkModExp-8                  	    1000	   1341863 ns/op
BenchmarkModExpWithSquaring-8      	 2000000	       754 ns/op
BenchmarkModExpGoBigInteger-8      	      50	  26960333 ns/op
BenchmarkModExpGoBigIntegerExp-8   	  500000	      2352 ns/op