The State of Go
Where we are in February 2016

Francesc Campoy
Gopher at Google
@francesc
campoy@golang.org

* Time flies

Go 1.4 is one year old (happy birthday!)

Go 1.5 is already 6 months old!

Go 1.6 to be released sometime in February.

Go 1.6 Candidate Release 1 was released on January 28th

* Notes

The slides are available on [[https://talks.golang.org/2016/state-of-go.slide]]

Most of the code examples won't run except locally and using Go 1.6.

The playground still runs Go 1.5.

* Agenda

Changes since Go 1.5:

- the language
- the standard library
- the runtime
- the tooling
- the community

* Changes to the language

* Changes to the language

None.

This is a feature.

* Changes to the standard library

* Changes to the standard library

A couple of new things, in order of excitement.

- net/http

- {text,html}/template

- sort

Also more speed and fewer bugs.

* net/http

If:

- you're using HTTPS

- and Go 1.6

you're using HTTP/2!

* HTTP/2

At a high level, HTTP/2:

- is binary, instead of textual
- is fully multiplexed, instead of ordered and blocking
- can therefore use one connection for parallelism
- uses header compression to reduce overhead
- allows servers to “push” responses proactively into client caches

.link https://http2.golang.org/gophertiles

* text/template

Imagine that given a slice of strings:

	[]string{"one", "two", "three"}

We want to write a template that will generate:

	<ul>
	<li>one</li>
	<li>two</li>
	<li>three</li>
	</ul>

What template would you write?

* text/template: first try

Naturally, I write this:

.play state-of-go/template/old.go /`/,/`/

But unfortunately it's not exactly what I want!

* text/template: let's fix it

We need to be careful with the line breaks.

.play state-of-go/template/fixed.go /`/,/`/

This works now, but ... I don't really like my code!

* text/template: meet {{- and -}}

Go 1.6 brings two new delimiters:

- `{{-`
- `-}}`

Similar to `{{` and `}}`, but _all_ white space on the `-` side will be trimmed.

The template:

	{{23 -}}
	<
	{{- 45}}

generates:

	23<45

* text/template: back to our problem

We can now have:

- the result we expected
- without sacrificing the readability of our templates.

.play state-of-go/template/new.go /`/,/`/

* text/template: the block action

Go 1.6 brings also a new action named `block`.

Let's see what it is useful for.

* Factoring out repetition in templates

Both `<ul>` share the same structure.

	{{define "presentation"}}
		Authors:
		<ul>
		{{range .Authors}}
			<li>{{.}}</li>
		{{end}}
		</ul>

		Topics:
		<ul>
		{{range .Topics}}
			<li>{{.}}</li>
		{{end}}
		</ul>
	{{end}}

Templates can be used to avoid repetition.

* Factoring out repetition with templates (cont.)

We can define a new template:

.code state-of-go/template/define.go /define "list"/,/^{{end}}/

And use it where needed:

.code state-of-go/template/define.go /define "presentation"/,/^{{end}}/

* Factoring out repetition with templates (cont.)

We can parse that template and execute it.

.play state-of-go/template/define.go /func main/,/^}/

* Template redefinition

We made also our template easier to reuse, as we can redefine `list`.

.play state-of-go/template/redefine.go /func main/,/^}/

* Meet the block action

The `block` action defines and executes a template in place.

.code state-of-go/template/blocks.go /define/,/`/

That template defined by `block` can be:

- referenced later by the same template,
- redefined with `define`.

* Why do we need it?

It is more compact when

- we're not factoring out repetition,
- but we need to provide an extension point.

We can make the following template more compact with `block`.

	{{define "content" .}}
		<h1>{{.Heading}}<h1>
		<p>{{.Content}}</p>
	{{end}}

	{{define "page"}}
		<title>{{.Title}}</title>
		<body>
		{{template "content" .}}
		</body>
	{{end}}

* Why do we need it? (cont.)

We can make the following template more compact with `block`.

	{{define "page"}}
		<title>{{.Title}}</title>
		<body>
		{{block "content" .}}
			<h1>{{.Heading}}<h1>
			<p>{{.Content}}</p>
		{{end}}
		</body>
	{{end}}

And still easily redefine `content`.

* sort.Sort is faster

`Sort` sorts your data by calling `Less`, `Swap`, and `Len`.

We reduced the number of comparisons and swaps by about 10%.

Sort `[]int` with Go 1.5

	BenchmarkSort_1-4       20000000              67.2 ns/op
	BenchmarkSort_10-4      10000000               227 ns/op
	BenchmarkSort_100-4       500000              3863 ns/op
	BenchmarkSort_1000-4       30000             52189 ns/op

Sort `[]int` with Go 1.6

	BenchmarkSort_1-4       20000000              64.7 ns/op
	BenchmarkSort_10-4      10000000               137 ns/op
	BenchmarkSort_100-4       500000              2849 ns/op
	BenchmarkSort_1000-4       30000             46949 ns/op

* sort.Sort is faster - plot

.image state-of-go/img/bench-sort.png _ 800

* Sort order and sort.Stable

Reminder: sort.Sort is not a _stable_ sort.

.play state-of-go/sort/unstable.go /byLength/,

Use `sort.Stable`:

.play state-of-go/sort/stable.go /func main/,

* Minor changes

.image state-of-go/img/minorchanges.png _ 900
.caption too many to discuss: find them [[https://golang.org/doc/go1.6#minor_library_changes][here]]

* Let's just discuss one

`time.Parse` is smarter!

.play state-of-go/time/time.go /func main/,/^}/


* Changes to the runtime

* Detection of concurrent map accesses

Detection of unsafe concurrent access to maps.

.play state-of-go/runtime/crash.go /const/,/Wait\(\)/

Outputs:

	fatal error: concurrent map read and map write
	fatal error: concurrent map writes

* Does it make it slower?

No!

Let's benchmark it - with a correct solution.

.code state-of-go/runtime/good/good.go /func count/,/^}/

* Benchmark results

Go 1.4 - GOMAXPROCS = 4

	BenchmarkCount_1         1000000              1862 ns/op
	BenchmarkCount_10         100000             21214 ns/op
	BenchmarkCount_100          1000           1602507 ns/op
	BenchmarkCount_1000           10         141712948 ns/op

Go 1.5 - GOMAXPROCS = 4

	BenchmarkCount_1-4       2000000               867 ns/op
	BenchmarkCount_10-4       200000              6909 ns/op
	BenchmarkCount_100-4        1000           1025092 ns/op
	BenchmarkCount_1000-4         20          94093719 ns/op

Go 1.6 - GOMAXPROCS = 4

	BenchmarkCount_1-4       2000000               750 ns/op
	BenchmarkCount_10-4       200000              6582 ns/op
	BenchmarkCount_100-4        2000           1113790 ns/op
	BenchmarkCount_1000-4         20          87998054 ns/op

* Benchmark results plot

.image state-of-go/img/bench4.png _ 800

* Benchmark results

Go 1.4 - GOMAXPROCS = 1

	BenchmarkCount_1         100000               1370 ns/op
	BenchmarkCount_10         20000               8622 ns/op
	BenchmarkCount_100          500             362725 ns/op
	BenchmarkCount_1000          50           31378803 ns/op

Go 1.5 - GOMAXPROCS = 1

	BenchmarkCount_1-4      2000000                776 ns/op
	BenchmarkCount_10-4      200000               6288 ns/op
	BenchmarkCount_100-4       3000             345037 ns/op
	BenchmarkCount_1000-4        50           31751625 ns/op

Go 1.6 - GOMAXPROCS = 1

	BenchmarkCount_1-4       2000000               767 ns/op
	BenchmarkCount_10-4       200000              6041 ns/op
	BenchmarkCount_100-4        5000            329328 ns/op
	BenchmarkCount_1000-4         50          30176034 ns/op

* Benchmark results plot

.image state-of-go/img/bench1.png _ 800

* Garbage Collector in Go 1.5

At [[https://www.youtube.com/watch?v=aiv1JOfMjm0][GopherCon 2015 Rick Hudson gave a presentation]] about the Go 1.5 low latency collector

.image state-of-go/img/gc345.png 500 _

* Garbage Collector in Go 1.6

At [[http://www.infoq.com/presentations/go-gc-performance][QCon SF in November Rick Hudson]] gave an updated presentation which showed this comparison of Go 1.5 to the upcoming Go 1.6

.image state-of-go/img/gc56.png 400 _

_Yes,_that_is_gigabytes_on_the_X_axis_

* Garbage Collector on tip

Right now it's even better!

.image state-of-go/img/gcgotip.png _ 600

* People loved it with Go 1.5

.image state-of-go/img/twitter1.png _ 550
.caption [[https://twitter.com/brianhatfield/status/634166123605331968][original tweet]]

* People love it even more with Go 1.6

.image state-of-go/img/twitter2.png _ 600
.caption [[https://twitter.com/brianhatfield/status/692778741567721473][original tweet]]

* Oops

.image state-of-go/img/twitter3.png _ 600
.caption [[https://twitter.com/bradfitz/status/692787593558118400][original tweet]] and [[https://www.youtube.com/watch?v=CduA0TULnow&t=1m29s][video]]

* New ports

Experimental ports to Linux on 64-bit MIPS (linux/mips64 and linux/mips64le).

Experimental port to Android on 32-bit x86 (android/386).

On Linux on little-endian 64-bit PowerPC (linux/ppc64le), Go 1.6 now supports cgo with external linking and is roughly feature complete.

On NaCl, Go 1.5 required SDK version pepper-41. Go 1.6 adds support for later SDK versions.

* Changes to the tooling

* The cgo tool

Go is garbage collected, can C and Go share memory?

In short:

- Go can pass a pointer to C
- the referenced memory can't have pointers to Go allocated memory
- C can't keep pointers to the memory after the call returns

In more detail:

- the `cgo` [[https://tip.golang.org/cmd/cgo/#hdr-Passing_pointers][docs]].

This is checked by the runtime at execution.

You could disable the checks, but you probably shouldn't.

* Sharing pointers between Go and C

.code state-of-go/cgo/main.go

Outputs:

	panic: runtime error: cgo argument has Go pointer to Go pointer

* The go tool

GO15VENDOREXPERIMENT is now enabled by default.

How does it work?

	/home/user/gocode/
	    src/
	        server-one/
	            main.go            (import "github.com/gorilla/mux")
	        server-two/
	            main.go            (import "github.com/gorilla/mux")
	            vendor/
	                github.com/
	                    gorilla/
	                        mux/
	                            ...

`server-one` uses the `mux` package in `$GOPATH/src/github.com/gorilla/mux`.

`server-two` uses the `mux` package in `vendor`.

* Vendoring demo

* go doc

Go 1.5 added the possibility of searching by name

	go doc math Pi

Go 1.6 defines priority of packages with import paths with less elements.

Non vendored packages appear first.

* go vet

Go vet warns if the code prints a function instead of its result.

.play state-of-go/govet/main.go

`go`vet` output:

	main.go:8: arg foo in Println call is a function value, not a function call

The warning can be removed using `%p` in the format string.

* The community

* The community

Code of Conduct announced on November 24th 2015

Go meetups:

- [[http://go-meetups.appspot.com]]

Women Who Go - 7 chapters already!

- [[http://www.womenwhogo.org]]

* Conferences:

- [[http://gophergala.com/][GopherGala]] Jan 22-24th (judging proposals now)
- [[https://fosdem.org/2016/][FOSDEM]] Right here, right now. Hello!
- [[http://gophercon.ae][GopherCon Dubai]], Feb 23rd
- [[http://www.gophercon.in/][GopherCon India]], Feb 19-20th
- [[https://gophercon.com/][Gophercon Denver]], Jul 11-13th
- [[http://2016.dotgo.eu/][dotGo]], Nov 9th

* Go 1.6 release party, February 17th

Go 1.6 ships soon!

Go meetups are organising to hold a [[https://github.com/golang/go/wiki/Go-1.6-release-party][release party]] on the 17th of February.

.image state-of-go/img/party-gopher.png _ 300
.caption Join the party!!!