What's new in Go 1.21 and 1.22

19 Fev 2024

Mauri de Souza Meneguzzo

About me

2

Let's Go!

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Go builds are now reproducible

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Supply Chain Attacks

https://xkcd.com/2347/

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VulnCheck v1.0.0

govulncheck cmd

go install golang.org/x/vuln/cmd/govulncheck@latest
govulncheck ./...

Vulnerability #1: GO-2023-2102
 HTTP/2 rapid reset can cause excessive work in net/http
    More info: https://pkg.go.dev/vuln/GO-2023-2102
    Module: golang.org/x/net
        Found in: golang.org/x/[email protected]
        Fixed in: golang.org/x/[email protected]
        Example traces found:
        #1: main.go:34:16: server.main calls gin.Engine.Run, which eventually calls
        http2.Server.ServeConn
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Go Toolchains

$ go version
go version devel go1.23-af5943f90c Sat Feb 17 23:25:55 2024 +0000 darwin/arm64
$ go env -w GOTOOLCHAIN=go1.22.0
$ go version
go version go1.22.0 darwin/arm64
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GOOS=wasip1 port

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Profile Guided Optimization

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How to capture a profile?

# tests or benchmarks
go test -cpuprofile=cpu.prof -bench=. .

# net/http/pprof
go tool pprof http://localhost:6060/debug/pprof/profile

# runtime/pprof
pprof.StartCPUProfile(f)
defer pprof.StopCPUProfile()
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Iterator Proposal

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Range over integer

package main


func main() {
    for i := range 5 {
        println(i)
    }
}

func BenchA(b *testing.B) {
    for i := 0; i < b.N; i++ {
        // ...
    }
}

func BenchB(b *testing.B) {
    for range b.N {
        // ...
    }
}
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Range over func, aka iterators

iter.Seq/iter.Seq2

package iter // import "iter"

// Seq is an iterator over sequences of individual values.
// When called as seq(yield), seq calls yield(v) for each value v 
// in the sequence, stopping early if yield returns false.
type Seq[V any] func(yield func(V) bool)

// Seq2 is an iterator over sequences of pairs of values, most commonly
// key-value pairs. When called as seq(yield), seq calls yield(k, v) for each
// pair (k, v) in the sequence, stopping early if yield returns false.
type Seq2[K, V any] func(yield func(K, V) bool)
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package main

import "iter"

func main() {
    var mySeq iter.Seq[int]
    mySeq = func(yield func(n int) bool) {
        for i := 0; i < 5; i++ {
            if !yield(i) {
                return
            }
        }
    }

    for v := range mySeq {
        println(v)
    }
}
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Dead Code Elimination

Go Blog about deadcode

$ go install golang.org/x/tools/cmd/deadcode@latest
$ deadcode ./...
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log/slog

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# implicit, simpler syntax
slog.Info("User logged in", "username", user.Name, "userid", user.ID)

# explicit, less memory allocs
slog.LogAttrs(context.Background(), slog.LevelInfo, "User logged in",
    slog.String("username", user.Name), slog.Int("userid", user.ID))

# zap for comparison
zapLogger.Info("User logged in",
    zap.String("username", user.Name),
    zap.Int("userid", user.ID))
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math/rand/v2

First V2 package in the stdlib

Read removed. Many people misused math/rand.Read as a secure random source instead of crypto/rand.Read

Outdated, slow algorithms in math/rand

//go:linkname Uint32 runtime.fastrand
func Uint32() uint32

//go:linkname Uint32n runtime.fastrandn
func Uint32n(n uint32) uint32
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net/http Routing enhancements

http.Handle("GET /posts/{id}", handlePost2)
// ...
idString := req.PathValue("id")
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Go 2 when?

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Go 1.23 so far

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Useful links

The Go home page.

Go blog

My talks are written with golang.org/x/tools/present

Find this talk at talks.mauri870.com

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Thank you

19 Fev 2024

Mauri de Souza Meneguzzo

[email protected]

https://github.com/mauri870

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