Iterate go routine with an anonymous function

[gonyyi]

What version of Go are you using (go version)?

--> go version go1.13 darwin/amd64

Does this issue reproduce with the latest release?

--> Yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/gonyi/Library/Caches/go-build"
GOENV="/Users/gonyi/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GONOPROXY="github.com/gonyyi"
GONOSUMDB="github.com/gonyyi"
GOOS="darwin"
GOPATH="/Users/gonyi/go"
GOPRIVATE="github.com/gonyyi"
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/jn/9zs9p73j7_gf3mzpdx4frmmd_05z01/T/go-build626678608=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

work := []string{"1mail", "2commute", "3coding", "4debugging", "5coffee"}
for _, v := range work {
	go func(){
		fmt.Println(v)
	}()
}

I was doing simple iteration of work thru channel with go routine.
I was expect WORK function will receive those 5 items, however, it was repeating likely last item in the work slice as below.

5coffee
5coffee
5coffee
5coffee
5coffee

But, instead of having anonymous in for-loop, if I call outside function, it gives expected result:

work := []string{"1homework", "2commute", "3coding", "4debugging", "5coffee"}
for _, v := range work {
	go fmt.Println(v)
	//go func(){
	//	fmt.Println(v)
	//}()
}

I think this is by the design, but I wonder if it makes more sense to have identical result..

What did you expect to see?

1homework
4debugging
5coffee
2commute
3coding

What did you see instead?

5coffee
5coffee
5coffee
5coffee
5coffee

[ALTree]

Hi,

the difference is that your first snippet is go-running a closure, while the second is not. (and the Println argument is evaluated immediately, even if the function is called later).

See: https://github.com/golang/go/wiki/CommonMistakes#using-goroutines-on-loop-iterator-variables

This is unlikely to change, so I'm closing this issue.

[D1CED]

If you run go vet—gos build in linter—it tells you about your mistake.

Here is your example in the playground which runs go lint when compiling: https://play.golang.org/p/7VnPfqpf_50