Prepares for a Go 1.21 upgrade. Pulled out of #478 but it's unrelated to the work there.
Addresses linting error like this:
cmd/demo/main.go:5:2: SA1019: "io/ioutil" has been deprecated since Go 1.19: As of Go 1.16, the same functionality is now provided by package [io] or package [os], and those implementations should be preferred in new code. See the specific function documentation for details. (staticcheck)
"io/ioutil"
^
ibc_test.go:7:2: SA1019: "io/ioutil" has been deprecated since Go 1.19: As of Go 1.16, the same functionality is now provided by package [io] or package [os], and those implementations should be preferred in new code. See the specific function documentation for details. (staticcheck)
"io/ioutil"
^
lib_test.go:7:2: SA1019: "io/ioutil" has been deprecated since Go 1.19: As of Go 1.16, the same functionality is now provided by package [io] or package [os], and those implementations should be preferred in new code. See the specific function documentation for details. (staticcheck)
"io/ioutil"
^
Prepares for a Go 1.21 upgrade. Pulled out of #478 but it's unrelated to the work there.
Addresses linting error like this: