Revert to go 1.20 and prepare for v1.19.1/v0.43.1

[dashpole]

See #708 (comment). We should set the go version in our go.mod to the minimum version we support, which is go 1.20.

Also, prepare for a patch release.

[dashpole]

cc @anuraaga

[anuraaga]

Thanks for the quick fix! 🙏

[codecov]

Codecov Report

Merging #717 (735798d) into main (92fd371) will increase coverage by 0.08%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #717      +/-   ##
==========================================
+ Coverage   69.66%   69.75%   +0.08%     
==========================================
  Files          38       38              
  Lines        4754     4754              
==========================================
+ Hits         3312     3316       +4     
+ Misses       1295     1291       -4     
  Partials      147      147              

Files Changed	Coverage Δ
exporter/metric/version.go	100.00% <100.00%> (ø)
exporter/trace/version.go	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[anuraaga]

Hi @dashpole - I randomly realized that opentelemetry-go-contrib targets 1.19 and depends on this library

https://github.com/open-telemetry/opentelemetry-go-contrib/blob/main/detectors/gcp/go.mod

AFAIK, this isn't really allowed, basically if someone tries to compile that library with 1.19 it will fail due to the missing errors.Join I think. Another side effect I have found is that go mod tidy automatically raises to the ceiling of all dependencies, which is actually 1.21 currently since that is still pointing to the older release (I added replace github.com/GoogleCloudPlatform/opentelemetry-operations-go/detectors/gcp v1.19.0 => github.com/GoogleCloudPlatform/opentelemetry-operations-go/detectors/gcp v1.19.1 to my project to fix that).

My project is now on 1.20 so not personally affected but wanted to share as it looks like it could be a problem for other users of the opentelemetry-go-contrib library.

[dashpole]

Ah, thanks. I think we are technically OK, as the detectors/gcp module doesn't use errors.Join. If it did, it would have failed presubmits when I bumped that in otel-go-contrib.

Contrib is using the patch release already, so you shouldn't need a replace: https://github.com/open-telemetry/opentelemetry-go-contrib/blob/3ad5a2c545431824f851c62be1c9253a59427c07/detectors/gcp/go.mod#L7