CI: Go 1.26 lint fails on deprecated io/ioutil usage

[dajiaohuang]

Description

The golangci-lint job for the v0.7.5 tag fails when the workflow resolves go-version: stable to Go 1.26.5. Staticcheck reports SA1019 because nocopy_readwriter_test.go still imports the deprecated io/ioutil package.

The same commit's compatibility, Windows, license-header, and spelling jobs pass; this lint failure leaves the release workflow red even though io.ReadAll has provided the same operation since Go 1.16.

Reproduction

1. Check out d63d249a3ba0dc9675a85c9762242247c368e500 (v0.7.5).
2. Run the repository's golangci-lint job with Go stable (the failing run resolved Go 1.26.5 and golangci-lint v1.64.8).
3. Observe:

nocopy_readwriter_test.go:22:2: SA1019: "io/ioutil" has been deprecated since Go 1.19

Failing job: https://github.com/cloudwego/netpoll/actions/runs/31067912905/job/92509503706

Expected behavior

The repository's lint job should pass on its configured stable Go toolchain.

Suggested fix

Replace ioutil.ReadAll with io.ReadAll and remove the deprecated import. This is test-only and does not change runtime behavior or supported APIs.

Environment

• Repository commit: d63d249a3ba0dc9675a85c9762242247c368e500
• Release: v0.7.5
• CI toolchain shown in the failing job: Go 1.26.5, golangci-lint v1.64.8, Ubuntu 24.04