Support Go 1.18

[StandoffVenus]

Small changes that recreate types introduced in Go 1.19's atomic so that this module may support Go 1.18.

[alphadose]

@StandoffVenus instead of _ sync.Locker why not use _ noCopy where

type noCopy struct{}

[StandoffVenus]

I can create and add that type - was just using sync.Locker because it already meets the no-copy check that go vet performs.

[alphadose]

@StandoffVenus yes but then you would be importing sync.Locker golang file too which would unnecessarily increase the binary size