Go module download flaky in CI: `local error: tls: bad record MAC`

In util self-tests, darwin-amd64 devscript [nosystemcrypto]:

https://dev.azure.com/dnceng-public/public/public%20Team/_build/results?buildId=1339663&view=logs&j=fd113e7d-47ec-577f-9a11-ec344e377922&t=cbf463b4-92dd-521e-9cf4-9afed2cbde43&l=99

---- Running command: /Users/runner/Library/Application Support/microsoft-go/go1.25.0-1/bin/go [/Users/runner/Library/Application Support/microsoft-go/go1.25.0-1/bin/go test ./...] in `eng/_util`
go: downloading github.com/golang-jwt/jwt/v5 v5.3.1
go: downloading github.com/google/go-github/v65 v65.0.0
go: downloading golang.org/x/oauth2 v0.36.0
go: downloading golang.org/x/text v0.35.0
go: downloading github.com/microsoft/azure-devops-go-api/azuredevops v1.0.0-b5
go: downloading github.com/google/uuid v1.6.0
# github.com/microsoft/go/_util/cmd/createbuildassetjson
/Users/runner/go/pkg/mod/github.com/microsoft/go-infra@v0.0.9/stringutil/stringutil.go:12:2: golang.org/x/text@v0.35.0: read "[https://proxy.golang.org/golang.org/x/text/@v/v0.35.0.zip"](https://proxy.golang.org/golang.org/x/text/@v/v0.35.0.zip%22): local error: tls: bad record MAC
# github.com/microsoft/go/_util/cmd/createbuildassetjson
/Users/runner/go/pkg/mod/github.com/microsoft/go-infra@v0.0.9/stringutil/stringutil.go:13:2: golang.org/x/text@v0.35.0: read "[https://proxy.golang.org/golang.org/x/text/@v/v0.35.0.zip"](https://proxy.golang.org/golang.org/x/text/@v/v0.35.0.zip%22): local error: tls: bad record MAC
# github.com/microsoft/go/_util/cmd/createbuildassetjson
/Users/runner/go/pkg/mod/github.com/microsoft/go-infra@v0.0.9/githubutil/auth.go:17:2: github.com/golang-jwt/jwt/v5@v5.3.1: Get "[https://proxy.golang.org/github.com/golang-jwt/jwt/v5/@v/v5.3.1.mod"](https://proxy.golang.org/github.com/golang-jwt/jwt/v5/@v/v5.3.1.mod%22): local error: tls: bad record MAC
# github.com/microsoft/go/_util/cmd/createbuildassetjson
/Users/runner/go/pkg/mod/github.com/microsoft/go-infra@v0.0.9/githubutil/fs.go:12:2: github.com/google/go-github/v65@v65.0.0: read "[https://proxy.golang.org/github.com/google/go-github/v65/@v/v65.0.0.zip"](https://proxy.golang.org/github.com/google/go-github/v65/@v/v65.0.0.zip%22): local error: tls: bad record MAC
# github.com/microsoft/go/_util/cmd/createbuildassetjson
/Users/runner/go/pkg/mod/github.com/microsoft/go-infra@v0.0.9/githubutil/githubutil.go:17:2: golang.org/x/oauth2@v0.36.0: read "[https://proxy.golang.org/golang.org/x/oauth2/@v/v0.36.0.zip"](https://proxy.golang.org/golang.org/x/oauth2/@v/v0.36.0.zip%22): local error: tls: bad record MAC
FAIL	github.com/microsoft/go/_util/cmd/createbuildassetjson [setup failed]
...

This would be using the stage 0 Go, which is go1.25.0-1 here.

We've seen a similar error in:

• curl: (56) OpenSSL SSL_read: error:1408F119:SSL routines:ssl3_get_record:decryption failed or bad record mac, errno 0
  https://github.com/microsoft/go/issues/657

This didn't occur in other jobs in the same CI run.

Start with the darwin-amd64 util self-test that runs go test ./... in eng/_util using stage 0 Go go1.25.0-1, and review the linked Azure log. Investigate the intermittent module downloads from proxy.golang.org and compare this run with other jobs in the same CI run. Done means the self-test no longer fails with tls: bad record MAC.