展开查看详情
1 .1/24/2019 The State of Go
The State of Go
Where we are in May 2017
Francesc Campoy
Google Developer Advocate
https://talks.golang.org/2017/state-of-go-may.slide#1 1/39
2 .1/24/2019 The State of Go
Recording
A recording of this talk is available here (https://www.youtube.com/watch?v=dyvpF0jF3AY&list=PLtLJO5JKE5YAeVbgwCkgUWyOBsMvZu4UB&index=1) .
2
https://talks.golang.org/2017/state-of-go-may.slide#1 2/39
3 .1/24/2019 The State of Go
Time ies
Go 1.7 is already 9 months old!
Go 1.8 was released on February 16th.
On May 1st we entered the release freeze for Go 1.9
Go 1.9 will be released early August.
3
https://talks.golang.org/2017/state-of-go-may.slide#1 3/39
4 .1/24/2019 The State of Go
Notes
The slides are available on talks.golang.org/2017/state-of-go-may.slide (https://talks.golang.org/2017/state-of-go-
may.slide)
Most of the code examples won't run except locally and using tip.
The playground runs Go 1.8. 4
https://talks.golang.org/2017/state-of-go-may.slide#1 4/39
5 .1/24/2019 The State of Go
Agenda
Changes since Go 1.8:
The Language
The Standard Library
The Runtime
The Tooling
The Community 5
https://talks.golang.org/2017/state-of-go-may.slide#1 5/39
6 .1/24/2019 The State of Go
Changes to the language
6
https://talks.golang.org/2017/state-of-go-may.slide#1 6/39
7 .1/24/2019 The State of Go
Codebase Refactoring (with help from Go)
Article written by Russ Cox link (https://talks.golang.org/2016/refactor.article)
Add new API
Code repairs
Remove old API
7
https://talks.golang.org/2017/state-of-go-may.slide#1 7/39
8 .1/24/2019 The State of Go
Gradual Code Repair
In reality, atomically changing all usages of an API is often impossible.
Stage 1 Add new API
Stage 2 Code repairs
Code repairs Code repairs
Code repairs
Stage 3 Remove old API
8
https://talks.golang.org/2017/state-of-go-may.slide#1 8/39
9 .1/24/2019 The State of Go
An example
Imagine we created a new package net/http/status.
First: create the new API
package status
const OK = http.StatusOK
Second: change each usage of http.StatusOK by status.OK.
if res.StatusCode != http.StatusOK {
if res.StatusCode != status.OK {
Third: remove the old API 9
https://talks.golang.org/2017/state-of-go-may.slide#1 9/39
10 .1/24/2019 The State of Go
Another example
Let's rename http.Get to http.DoGetPleaseAndThanks.
First: create the new API
func DoGetPleaseAndThanks(url string) (*http.Response, error) {
return Get(url)
}
Second: change each usage of http.Get to http.DoGetPleaseAndThanks.
res, err := http.Get("https://golang.org")
res, err := http.DoGetPleaseAndThanks("https://golang.org")
Third: remove the old API 10
https://talks.golang.org/2017/state-of-go-may.slide#1 10/39
11 .1/24/2019 The State of Go
One last example
Let's move http.Client to http.Applicant.
First: create the new API
type Applicant Client
Applicant has no methods.
Both types are convertible.
type Applicant struct { Client }
Applicant has all the methods of Client
The types are not convertible. 11
https://talks.golang.org/2017/state-of-go-may.slide#1 11/39
12 .1/24/2019 The State of Go
Alias declarations
An alias declaration is a new kind of type declaration.
type Applicant = http.Client
Both types are equivalent and completely interchangeable.
type conversion is not needed
can't declare methods on the alias declaration
type Applicant = http.Client
func main() {
fmt.Printf("%T", Applicant{})
} Run
12
https://talks.golang.org/2017/state-of-go-may.slide#1 12/39
13 .1/24/2019 The State of Go
Quaternions
issue #19813(https://golang.org/issue/19813) 13
https://talks.golang.org/2017/state-of-go-may.slide#1 13/39
14 .1/24/2019 The State of Go
The Standard library
14
https://talks.golang.org/2017/state-of-go-may.slide#1 14/39
15 .1/24/2019 The State of Go
A Twitter Poll
twitter poll(https://twitter.com/francesc/status/863514399486623744) 15
https://talks.golang.org/2017/state-of-go-may.slide#1 15/39
16 .1/24/2019 The State of Go
math/bits
Package bits (https://tip.golang.org/pkg/math/bits/#Len16) implements bit counting and manipulation functions for
the predeclared unsigned integer types.
Added to the standard library with proposal #18616 (https://golang.org/issue/18616) .
LenXX, OnesCountXX
ReverseXX, ReverseBytesXX
RotateLeftXX
LeadingZerosXX, TrailingZerosXX
fmt.Printf("%d (%b) has %d bits set to one\n", n, n, bits.OnesCount(n))
fmt.Printf("%d reversed is %d\n", n, bits.Reverse(n))
fmt.Printf("%d can be encoded in %d bits\n", n, bits.Len(n)) Run
16
https://talks.golang.org/2017/state-of-go-may.slide#1 16/39
17 .1/24/2019 The State of Go
sync.Map
A new type has been added to the sync package with proposal #18177 (https://golang.org/issue/18177) .
sync.Map (https://tip.golang.org/pkg/sync/#Map) is a concurrent map with amortized-constant-time loads,
stores,and deletes.
the zero map is valid
it must not be copied (use pointers) 17
https://talks.golang.org/2017/state-of-go-may.slide#1 17/39
18 .1/24/2019 The State of Go
sync.Map code sample
func main() {
var m sync.Map
for i := 0; i < 3; i++ {
go func(i int) {
for j := 0; ; j++ {
m.Store(i, j)
}
}(i)
}
for i := 0; i < 10; i++ {
m.Range(func(key, value interface{}) bool {
fmt.Printf("%d: %d\t", key, value)
return true
})
fmt.Println()
time.Sleep(time.Second)
}
} Run
18
https://talks.golang.org/2017/state-of-go-may.slide#1 18/39
19 .1/24/2019 The State of Go
html/template panic on prede ned escaper
What do you expect this code (https://play.golang.org/p/-z5rZilH1F) to print?
type Foo struct{ Bar string }
func main() {
tmpl, err := template.New("home").Parse(`
<a title={{.Bar | html}}>
`)
if err != nil {
log.Fatalf("could not parse: %v", err)
}
foo := Foo{"haha onclick=evil()"}
if err := tmpl.Execute(os.Stdout, foo); err != nil {
log.Fatalf("could not execute: %v", err)
}
} Run
Prede ned escapers in html template create a security concern.
Since 1.9 Execute will panic. 19
https://talks.golang.org/2017/state-of-go-may.slide#1 19/39
20 .1/24/2019 The State of Go
os.Exec
Let's imagine that we have a command getenv that prints an environment variable
using os.Getenv.
func main() {
if len(os.Args) != 2 {
fmt.Printf("use %s varname\n", os.Args[0])
os.Exit(1)
}
fmt.Println(os.Getenv(os.Args[1]))
}
We can run it as follows:
$ foo=bar getenv foo
bar
20
https://talks.golang.org/2017/state-of-go-may.slide#1 20/39
21 .1/24/2019 The State of Go
os.Exec
What do you expect this code to print?
func main() {
cmd := exec.Command("getenv", "foo")
cmd.Env = append(os.Environ(), "foo=newbar")
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
if err := cmd.Run(); err != nil {
log.Fatal(err)
}
}
bar, or newbar? 21
https://talks.golang.org/2017/state-of-go-may.slide#1 21/39
22 .1/24/2019 The State of Go
another Twitter poll
Twitter poll(https://twitter.com/francesc/status/863791506934472705) 22
https://talks.golang.org/2017/state-of-go-may.slide#1 22/39
23 .1/24/2019 The State of Go
os.Exec
Cmd.Start now removes duplicates of environment variables, keeping the last one.
This code does what one expects:
cmd := exec.Command("prog")
cmd.Env = append(os.Environ(), "FOO=bar")
23
https://talks.golang.org/2017/state-of-go-may.slide#1 23/39
24 .1/24/2019 The State of Go
The Runtime
24
https://talks.golang.org/2017/state-of-go-may.slide#1 24/39
25 .1/24/2019 The State of Go
Benchmarks
note: values over 1.0 mean tip is faster
note: uno cial benchmark ran on my laptop while playing YouTube videos 25
https://talks.golang.org/2017/state-of-go-may.slide#1 25/39
26 .1/24/2019 The State of Go
More runtime
Garbage Collector
New algorithm for large object allocation
Better performance and increased determinism for large (+50GB) heaps
DWARF (https://en.wikipedia.org/wiki/DWARF)
Ongoing e ort to improve the generated DWARF information.
This will help debuggers, among other tools. 26
h li
l
https://talks.golang.org/2017/state-of-go-may.slide#1 26/39
27 .1/24/2019 The State of Go
The Tooling
27
il b
https://talks.golang.org/2017/state-of-go-may.slide#1
! 27/39
28 .1/24/2019 The State of Go
go compiler: better errors!
Better error messaging for Allman style braces.
package main
func main()
{
fmt.Println("that ain't gonna compile")
}
With go 1.8:
fail/main.go:4: syntax error: unexpected semicolon or newline before {
With go 1.9:
fail/main.go:3:6: missing function body for "main"
fail/main.go:4:1: syntax error: unexpected semicolon or newline before {
28
il
https://talks.golang.org/2017/state-of-go-may.slide#1
d l df 28/39
29 .1/24/2019 The State of Go
go compiler: more modular and faster
The compiler has been refactored into multiple packages.
cmd/go/internal/...
Issue #17639 (https://golang.org/issue/17639) made parsing concurrent.
The compiler is faster as a result. 29
t t
https://talks.golang.org/2017/state-of-go-may.slide#1 29/39
热门城市
