go: update to 1.21.0

[herbygillot]

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[macportsbot]

Notifying maintainers:
@ci42 for port go.

[jpeeler]

@herbygillot I noticed that go.env was missing in /opt/local/lib/go. After putting the file in place, GOPROXY functioned as expected: golang/go#61928.

[saj]

I'm seeing the same problem on go@1.21.0_0.

% go mod init foo
go: creating new go.mod: module foo
% go get golang.org/x/exp/rand
go: golang.org/x/exp/rand: GOPROXY list is not the empty string, but contains no entries

To elaborate on jpeeler's workaround...

curl -LSsf -o /opt/local/lib/go/go.env https://raw.githubusercontent.com/golang/go/go1.21.0/go.env

go.env was added in upstream CR 462198 and landed in 7aa85e; first appeared in go1.21rc1.

golang/go#61928 was closed by the reporter but I wonder whether this is an upstream bug.
readEnvFile tolerates ENOENT; it is only later when the error is returned.

len(proxyOnce.list) == 0

Is that not expected if a downstream chooses to disable GOPROXY=?

In any case, I think we probably want to copy go.env into the destroot.

---

Edit: Maybe an empty GOPROXY is invalid by definition.

https://go.dev/ref/mod#resolve-pkg-mod

When the go command looks up a new module for a package path, it checks the GOPROXY environment variable, which is a comma-separated list of proxy URLs or the keywords direct or off. A proxy URL indicates the go command should contact a module proxy using the GOPROXY protocol. direct indicates that the go command should communicate with a version control system. off indicates that no communication should be attempted.

[herbygillot]

@jpeeler @saj Thank you both for catching and commenting on this, tracking this in MacPorts Trac here: https://trac.macports.org/ticket/67961

This PR is meant to fix this: #19892

[herbygillot]

This issue should now be fixed.