D'oh!
This is a known issue. (I should have checked before posting my original
message).
https://github.com/golang/go/issues/52317
So if you are an OSX user, then either download for source
Or keep using 1.18 until https://github.com/golang/go/issues/52317 is
resolved.
On Wednesday, 13 April
Thank for the new release...
I may be looking in the wrong place, but the darwin binaries for 1.18.1
appear to be missing.
https://go.dev/doc/install when installing on a mac shows an installer
button labeled "Download Go for Mac"
which links to https://go.dev/dl/undefined which gives a 404