doc/go1.16: document new go/build/constraint package

[dmitshur]

The new go/build/constraint package in Go 1.16 should be documented in the final Go 1.16 release notes as part of #40700.

CC @rsc.

[ianlancetaylor]

Why do I not see anything from the go/build/constraint package in api/go1.16.txt?

[ianlancetaylor]

Hmmm, they are printed by the API check but did not wind up in go1.16.txt or next.txt.

[dmitshur]

@ianlancetaylor Please see #43407 (comment) and https://golang.org/cl/287412.

[ianlancetaylor]

Thanks, looks like go/build/constraint landed January 8, so we need some mechanism for checking for new additions late in the release cycle. I, at least, never noticed it.

[gopherbot]

Change https://golang.org/cl/287472 mentions this issue: doc/go1.16: document go/build/constraint package

[dmitshur]

Thanks, looks like go/build/constraint landed January 8, so we need some mechanism for checking for new additions late in the release cycle. I, at least, never noticed it.

I agree. I've CCed you on issue #43956 which is about resolving that and contains some more details.