it defaults to `panicnil=0`, making `panic(nil)` a run-time error.
Using `panicnil=1` restores the behavior of Go 1.20 and earlier.

When compiling a work module or workspace that declares
an older Go version, the Go toolchain amends its defaults
to match that older Go version as closely as possible.
For example, when a Go 1.21 toolchain compiles a program,
if the work module's `go.mod` or the workspace's `go.work`

will succeed.
Such code should use a non-blocking receive instead.

These new behaviors are only enabled when the main Go program
is in a module with a `go.mod` `go` line using Go 1.23.0 or later.
When Go 1.23 builds older programs, the old behaviors remain in effect.
The new [GODEBUG setting](/doc/godebug) [`asynctimerchan=1`](/pkg/time/#NewTimer)
can be used to revert back to asynchronous channel behaviors

<a href="#Integer_literals">integer literals</a>.
Source code containing an integer literal such as <code>0b1011</code>
will be rejected if the implied or required language version used by
the compiler is older than Go 1.13.
</p>

<p>
The following table describes the minimum language version required for
features introduced after Go 1.
</p>

<h4 id="Go_1.9">Go 1.9</h4>
<ul>
<li>