new-in-go.org

What’s New in Go (November 2023)

Who?

• I’m Terin!
• Software Developer at Cloudflare
• Been developing in Go since Go 1.4

Point Releases

Go 1.21.4 and Go 1.20.11

• Fix to net/http’s Pusher implementation causing connection resets in Firefox and Safari.
• Various bug fixes to the compiler, linker, and runtime.

Two security fixes to path/filepath package on Windows:

• Incorrect parse of path prefix \??\, leading to arbitrary file access.
• Incorrect detection of reserved file names (eg, COM1 and LPT1) as local in some circumstances.

Road to Go 1.22

Revised API for math/rand/v2

• First standard library package to get a “v2” redesign.
• Top-level functions were modified to make it easier to use.

Focsed on being a psuedo-random number generate for non-cryptographic use cases (eg, simulations).

• Removes ability to get random bytes by removing Rand.Read.
• Removes top-level Seed, Rand.Seed, and Source.Seed.
• Replaces Source.Int63 with Source.Uint64.
• Removes the original Linear-Feedback Shift Register source, and adds PCG-DXSM and ChaCha8 as source options.

Experiment to extend for-range

• Add compiler support for new for-range loops behind GOEXPERIMENT=range flag.

range over integers

The C-style loop over integers like

for x := 0; x < 10; x++ { }

would become

for x := range 10 {
	// x will be in the range 0..n-1
}

range over functions

Allows looping over coroutine functions.

type f function(yield func(T1, T2) bool) bool

for x, y := range f {
	// the control statements "break", "continue", "return"
	// still work like normal within this for loop.
}

• See Russ Cox’s Coroutines with Go blog post for more details.

TCP Keepalive Configuration

• Go sets the TCP keepalive timeout (TCP_KEEPINTVL) to 15 seconds.
  • Setting KeepAlive on net.Dialer allows sending keepalives more often.
  • Reports from mobile users that this keeps devices and radios awake.
• Proposal adds KeepAliveConfig option to net.Dialer, and adds SetKeepAliveConfig on TCPConn.

Example configuring an HTTP client

client := http.Client{
	Transport: &http.Transport{
		DialContext: &net.Dialer{
			KeepAliveConfig: net.KeepAliveConfig{
				Enable:   true,
				Idle:     5*time.Second,
				Interval: 30*time.Second,
				Count:    3,
			}
		}
	}
}

Adds unique package to intern values

• Allows creating a weak reference to values by retaining references to Lisp-like symbols.
• Brings a version of go4.org/intern to the standard library.
• Can be used to weakly store one-copy of a string, with fast comparison.

func (ip Addr) WithZone(zone string) Addr {
    ip.z = unique.Make(zone)
}

Miscellenous Proposals

• Support for flaky tests
• Store debugging info in separate DWARF files on macOS