gotools.bash prints Go tools that can be updated.
By default, it checks tools in the Go tool's default go install location, so that you can go install $(gotools.bash). (It turns out that this doesn't actually work, though, you need to do something like for cmd in $(gotools.bash); do go install -v $cmd; done instead.)
Since the go install location is $GOBIN, you can choose a different location to check by invoking like GOBIN=/usr/local gotools.bash.
There are two senses of "can be updated" that the script checks for.
If a tool was built with a different version of Go than go, the script suggests reinstalling it at its current version.
Otherwise, if the configured module proxy reports a different version as the latest than the installed version of the command, the script suggests reinstalling it with the reported latest version.