support Go 1.22.0

[jmhodges]

CodeQL runs currently fail when the go.mod is set to version 1.22.0. Go 1.22.0 was released on 2024-02-06.

The error message (as seen in this run) of the failing step ("Setup Go") is:

go: download go1.22 for linux/amd64: toolchain not available
Error: Command failed: go env GOPATH

However, if you look up earlier in the "Configure" step, there's a message emitted from identify-environment.sh:

The version of Go found in the `go.mod` file (1.22) is above the supported range (1.11-1.21). The version of Go installed in the environment (1.20.14) is below the maximum supported version (1.21). Requesting the maximum supported version of Go (1.21).

[smowton]

You're right that full Go 1.22 support will be coming very soon, but the existing partial support will actually work 90% of the time.

However, what's happening here is Go 1.21+ know how to themselves download a more modern version of Go if specified in the go.mod file, and will do so in response to any go command being run in the context of a go.mod specifying either a go or toolchain directive specifying a more modern version... except this requires us to specify not go 1.22 (since there is no release by that name) but go 1.22.0 (which is the name of a release). The go command will then download and use that version, and the warnings about Go 1.22 not being 100% supported yet should be irrelevant except where your code uses any language or library feature not present in Go 1.21.