Files in this directory are data for Go's API checker ("go tool api", in src/cmd/api).

Each file is a list of of API features, one per line.

go1.txt (and similarly named files) are frozen once a version has been
shipped. Each file adds new lines but does not remove any.

except.txt lists features that may disappear without breaking
true compatibility. The only package there is text/template/parse.

next.txt is the only file intended to be mutated. It's a list of
features that may be added to the next version. It only affects
warning output from the go api tool.