says `go` `1.20`, then the program defaults to `panicnil=1`,
matching Go 1.20 instead of Go 1.21.

Because this method of setting GODEBUG defaults was introduced only in Go 1.21,
programs listing versions of Go earlier than Go 1.20 are configured to match Go 1.20,
not the older version.

To override these defaults, a main package's source files
can include one or more `//go:debug` directives at the top of the file

The new [ParseCookie] function parses a Cookie header value and
returns all the cookies which were set in it. Since the same cookie
name can appear multiple times the returned Values can contain
more than one value for a given key.

The new [ParseSetCookie] function parses a Set-Cookie header value and

## Tools {#tools}

### Go command {#go-command}

Setting the `GOROOT_FINAL` environment variable no longer has an effect
([#62047](https://go.dev/issue/62047)).
Distributions that install the `go` command to a location other than
`$GOROOT/bin/go` should install a symlink instead of relocating
or copying the `go` binary.

### Vet {#vet}

The `go vet` subcommand now includes the