Thread by @mvdan_

Here's a list of some changes coming in #golang 1.19! The first beta will be out in a month, and the final release in early August.

Live tweeting from @GolangSheffield! Each change with a link, so you can read more.

1.18 shipped generics, which made it a large release that arrived six weeks late.

This means 1.19 got less development time than usual, to be able to release on time. The feature freeze is this week.

Starting out, lots of fixes and tweaks for type parameters AKA generics!

Some are being backported to Go 1.18, and some are still in progress. Overall, more polish.

What about major features?

First, runtime.SetMemoryLimit to provide the garbage collector with a soft memory limit!

Similar to GOGC, but based on total size rather than a percentage. github.com/golang/go/issu…

The runtime now increases the limit of open files!

On some Linux systems, the default "soft" limit is 1024, but can be increased up to the "hard" limit.

github.com/golang/go/issu…

The race detector is now 2-10x faster than before, thanks to ThreadSanitizer's new v3 runtime!

github.com/golang/go/issu…

We have a new Address Sanitizer with -asan, a new companion to -race and -msan!

It can catch some classes of memory errors, especially when handling memory manually via CGo.

github.com/golang/go/issu…

The net package now uses EDNS to increase the DNS packet size, to adhere to modern DNS standards and implementations.

This should help with problems with some DNS servers.

use EDNS to increase DNS packet size - github.com/golang/go/issu…

The "unix" build tag now exists, so no more "// +build darwin dragonfly freebsd linux netbsd openbsd solaris"!

Note that "*_unix.go" is not recognized, for backwards compatibility with existing files.

github.com/golang/go/issu…

os/exec now consistently sets the PWD environment variable to avoid confusion.

This also means a new Cmd.Environ method to get the applied environment.

github.com/golang/go/issu…

What about the standard library?

Starting with flag.TextVar, which allows making a flag out of any encoding.TextMarshaler and Unmarshaler!

github.com/golang/go/issu…

net/url also gains JoinPath, akin to path.Join but without breaking "//" in URLs.

github.com/golang/go/issu…

time.Duration gains an Abs method, to make some time comparisons easier to write.

github.com/golang/go/issu…

encoding/binary gains AppendByteOrder, to encode integers in the "append" style.

This can be more convenient, by not needing an extra temporary buffer.

github.com/golang/go/issu…

Similarly, encoding/binary also gains AppendVarint and AppendUvarint.

github.com/golang/go/issu…

To round off the list, performance!

Big map literals are now initialized much faster than before, saving time when their code is run.

github.com/golang/go/issu…

The compiler now propagates more variables that it can prove to have a constant value.

This makes the Go binary 0.04% smaller, and should produce marginal speed gains.

go-review.googlesource.com/c/go/+/403735

bytes.Buffer now grows more efficiently, thanks to the "append" builtin.

github.com/golang/go/issu…

reflect.Value now allows calling the Bytes method on addressable byte arrays.

Before, one had to use the Slice method, which allocates.

github.com/golang/go/issu…

And finally, io's MultiReader and NopCloser now forward WriteTo method calls.

github.com/golang/go/issu…
github.com/golang/go/issu…