# 'go mod edit' opportunistically locks the side-lock file in the module cache,
# for compatibility with older versions of the 'go' command.
# It does not otherwise depend on the module cache, so it should not
# fail if the module cache directory cannot be created.

[root] skip

mkdir $WORK/readonly
chmod 0555 $WORK/readonly
env GOPATH=$WORK/readonly/nonexist

go mod edit -go=1.17

-- go.mod --
module example.com/m