Short program to benchmark square and 4th powers of float64 using multiplication vs math.Pow():
Results on a i7-7700K is overclocked to 5GHz in single-threaded loads:
>go test -bench .
goos: windows
goarch: amd64
pkg: powtest
BenchmarkSquareByMultiplying-8 2000000000 0.43 ns/op
BenchmarkSquareWithPow-8 100000000 21.4 ns/op
BenchmarkQuadByMultiplying-8 2000000000 0.21 ns/op
BenchmarkQuadWithPow-8 50000000 22.0 ns/op