Adopt Go toolchains for language-version-control

[Groxx]

Go 1.21 brought us "toolchains":
We can now describe the version we want, and the Go CLI will automagically download, install, and use that version, with no extra effort. It should give us a MUCH more reliable way to ensure identical builds and formats and whatnot, and all us devs will auto-switch as we jump between git SHAs.

So let's use that!

This does a few things:

• requires Go 1.21+ to be your go version to work on Cadence.
  • this does not force our users to use 1.21+, that's still 1.20, controlled by the go 1.20 lines. just development in this workspace.
• sets a go.work toolchain (if there's a go.work file, toolchains in individual go.mod files are ignored)
  • not all IDEs follow this. we could set it + lint it in the go.mod files too if it helps, it just won't have any effect on CLI go use so it may be misleading.
• exports GOTOOLCHAIN=... inside the Makefile, so ALL makefile-driven builds by everyone use exactly the same version (you can override this with an explicit GOTOOLCHAIN)
• updates our dockerfiles (it would just download [wrong version in docker image] and then auto-download the right one, which is a waste of time)
• adds a lint script to ensure ^ all that stays up to date

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For future upgrades, upgrading the toolchain should be very simple:

• change go.work to a new toolchain version
  • everything now uses the new language version, tools and binaries will rebuild, etc.
• make lint or make pr or CI will tell you to change the Dockerfiles / other locations, if you don't git grep -F 1.22.3 to find and update those first.

And temporarily trying a different version to check a bug / performance / try the new version is:

• GOTOOLCHAIN=go1.23.4 make whatever and it'll do exactly that (except for the version check in make lint)
• you may want to make clean as well, to rebuild tools if that's relevant
  • they will not automatically rebuild with this env var changing. they could, if we used .build/go1.23.4/etc folders, if we want that.

[Groxx]

❯ GOTOOLCHAIN=auto make
Makefile:46: warning: your Go toolchain is explicitly set to GOTOOLCHAIN=auto, ignoring go.work version go1.22.3...

which seems pretty good.

CI has a bunch of lines like

Makefile:46: warning: your Go toolchain is explicitly set to GOTOOLCHAIN=local, ignoring go.work version go1.22.3...

which could be handled more quietly by querying go version... but that'd potentially force a download before it responds, which could cause a big surprising lag if it happened on a dev's machine.

but maybe. or maybe there's a different, better option somewhere. not sure at the moment.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.01%. Comparing base (2f08de5) to head (aedc290).

Additional details and impacted files

see 8 files with indirect coverage changes

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[coveralls]

Pull Request Test Coverage Report for Build 018fb74e-8f78-4b91-acc2-561eb11fc052

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 46 unchanged lines in 9 files lost coverage.
• Overall coverage decreased (-0.02%) to 69.503%

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Files with Coverage Reduction	New Missed Lines	%
service/history/queue/timer_queue_processor_base.go	1	77.66%
common/cache/lru.go	2	92.89%
service/history/replication/task_processor.go	2	81.25%
common/archiver/filestore/historyArchiver.go	4	80.95%
service/matching/tasklist/task_list_manager.go	4	76.09%
service/frontend/api/handler.go	6	62.2%
service/history/task/transfer_standby_task_executor.go	9	85.8%
service/history/engine/engineimpl/poll_mutable_state.go	9	74.16%
service/frontend/wrappers/metered/metered.go	9	63.18%

Totals
Change from base Build 018facb4-1556-4d0a-a60a-2fec545c95e9:	-0.02%
Covered Lines:	102502
Relevant Lines:	147479

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💛 - Coveralls