Go Release 1.20

Introduce changes in Go 1.20 to our audience.

Transcript

1. G r le se 1.20
   L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 1
   

   View Slide

2. T me in
   4 1 .1.2 - 1.2 R
   4 1 .1.2 - d e s
   4 1.2.2 - 1.2 r d!
   4 4-5.2.2 - F 2 - M E - S G
   4 6.2.2 - u o'G - 1.2 o ! ...
   4 1 .2.2 - 1.2 .1
   4 1 .2.2 - T #2 - W 's e 1.2
   4 2 .2.2 - u m ;-)
   L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 2
   

   View Slide

3. R le se ot s
   4 g .d /d /g .2
   4 g .2
   L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 3
   

   View Slide

4. L ng ag c an es
   4 g s: comparable s i c {}
   4 n n SliceData, String, StringData unsafe
   p
   4 d c i o a s a
   4 e o w a e s n s e
   a c d
   L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 4
   

   View Slide

5. G ne ic : C mp ra le on tr in
   func SumIntsOrFloats[K comparable, V int64 | float64](m map[K]V) V {
   var s V
   for _, v := range m {
   s += v
   }
   return s
   }
   4 N s y c b interface{}, l r u
   p r !
   L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 5
   

   View Slide

6. S mp if s nt x li e -> a ra
   s 1.1
   slice := []int{1,2,3, 4}
   array := (*[4]byte)(slice)
   s 1.2
   slice := []int{1,2,3, 4}
   array := [4](slice)
   L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 6
   

   View Slide

7. T ol mp ov me ts
   4 c o s p l
   4 g b , i a -pgo n -cover a
   4 c d d d
   4 g e i m
   L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 7
   

   View Slide

8. G v t
   package main
   import (
   "fmt"
   "time"
   )
   func main() {
   now := time.Now()
   now.Format("2006-02-01")
   fmt.Println(now)
   }
   $ go vet main.go
   # command-line-arguments
   ./main.go:10:14: 2006-02-01 should be 2006-01-02
   L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 8
   

   View Slide

9. C ve p o l s n ac ag l ve
   go test -coverprofile=...
   4 h ://g .d /t /c e/
   L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 9
   

   View Slide

10. B il w th ov r
    go build -cover -o myprogram.exe .
    go build -cover -o myprogramMorePkgs.exe -coverpkg=io,mydomain.com,rsc.io/quote .`
    L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 1
    

    View Slide

11. R n o et at
    mkdir somedata
    GOCOVERDIR=somedata ./myprogram.exe
    GOCOVERDIR=somedata ./myprogram.exe --flag
    4 y a u i m e t , c r
    p l
    L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 1
    

    View Slide

12. W rk ng it c ve ag d ta l s
    go tool covdata -i= ...flags...
    go tool covdata percent -i=somedata
    go tool covdata merge -i=windows_datadir,macos_datadir -o merged
    L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 1
    

    View Slide

13. S an ar l br ry dd ti ns
    4 T e crypto/ecdh p p s e t s o E c C
    D e-H e e e e S c n C 5 .
    4 T e f n e .J r e w g s e
    w a o d a h e p i n h Unwrap()
    []error m .
    4 T e http.ResponseController p p s a e d p -
    r f n o h h http.ResponseWriter i c .
    4 T httputil.ReverseProxy f i p i s e R o
    f n, s d h p s D r h .
    L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 1
    

    View Slide

14. S an ar l br ry dd ti ns I
    4 T e context.WithCancelCause f n p s a
    c a c t a g e . a e a r e
    b c h e context.Cause f n.
    4 T e os/exec.Cmd e C n W a s h
    b r h m e t a t C c d
    i p e .
    4 I time p e a e e c t DateTime,
    DateOnly n TimeOnly
    L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 1
    

    View Slide

15. E ro s
    Unwrap() error
    Unwrap() []error
    wrapsErr := fmt.Errorf("... %w ...", ..., err, ...)
    if errors.Is(err, fs.ErrExist)
    err1 := errors.New("err1")
    err2 := errors.New("err2")
    err := errors.Join(err1, err2)
    L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 1
    

    View Slide

16. R sp ns Co tr ll r
    func RequestHandler(w ResponseWriter, r *Request) {
    rc := http.NewResponseController(w)
    rc.SetWriteDeadline(time.Time{}) // disable Server.WriteTimeout when sending a large response
    io.Copy(w, bigData)
    }
    4 G I : n /h : a m a
    t s H
    L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 1
    

    View Slide

17. h tp.R ve se ro y
    proxyHandler := &httputil.ReverseProxy{
    Rewrite: func(r *httputil.ProxyRequest) {
    r.SetURL(outboundURL) // Forward request to outboundURL.
    r.SetXForwarded() // Set X-Forwarded-* headers.
    r.Out.Header.Set("X-Additional-Header", "header set by the proxy")
    },
    }
    4 T e R e s e h i g r
    f h o g r n d a e h m
    t k e w a s f i p .
    L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 1
    

    View Slide

18. c nt xt.W th an el au e [^1]
    ctx, cancel := context.WithCancelCause(parent)
    cancel(myError)
    ctx.Err() // returns context.Canceled
    context.Cause(ctx) // returns myError
    L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 1
    

    View Slide

19. o /e ec.C d
    ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
    defer cancel()
    if err := exec.CommandContext(ctx, "sleep", "5").Run(); err != nil {
    // This will fail after 100 milliseconds. The 5 second sleep
    // will be interrupted.
    }
    4 T e m e Cancel n WaitDelay s h b r
    o h m e t a t C c d t
    p e t I/O p s l e a c p .
    L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 1
    

    View Slide

20. C tP e x / C tS x
    s := "https://github.com"
    str, ok := strings.CutPrefix(s, "https://")
    if ok {
    fmt.Println(str)
    } else {
    fmt.Println(s)
    }
    L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 2
    

    View Slide

21. T me on ta t pd te
    DateTime = "2006-01-02 15:04:05"
    DateOnly = "2006-01-02"
    TimeOnly = "15:04:05"
    L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 2
    

    View Slide

22. I pr ve p rf rm nc
    4 C r n g c o i m v
    r m o d n i d o P
    p a 2%.
    4 W s c t n c t t e
    b i m 1 %. i b b
    s c n t 1.1 .
    L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 2
    

    View Slide

23. R fe en es
    C M. J n i s p r g a r 1.2
    4 h ://b .c h .n /p /2 /g -1 -l e-
    c /
    4 h ://b .c h .n /p /2 /g -1 -a -
    e -r e l /
    4 h ://b .c h .n /p /2 /g -1 -m -
    f s/
    L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 2
    

    View Slide

24. w w.g me tu pr gu .c
    @g me tu pr gu @f ss od n.o g
    L v P c (P S ) - @a @h r .i - M P #1 , 2 .2. 2 2
    

    View Slide