Go minimum version changed to 1.20 due to use of sync.Map#CompareAndSwap

[lukestoward]

I noticed recently due to issues compiling that 0.119.0 changed the minimum version of Go required to use this module from 1.18 (as stated in the go.mod to 1.20. This is due to an added usage of the sync.Map#CompareAndSwap method, which was added to the standard library in Go 1.20.

Looking through the changes, I believe this line is the cause. Please can you update the go.mod to state the minimum Go version is 1.20 or enable the code to be compiled with 1.18 again.