Abnormal number increment

[storyicon]

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

$ go version
go version go1.16.3 windows/amd64

Does this issue reproduce with the latest release?

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

go env Output

$ go env
set GO111MODULE=
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\storyicon\AppData\Local\go-build
set GOENV=C:\Users\storyicon\AppData\Roaming\go\env
set GOEXE=.exe
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=D:\Go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=D:\Go
set GOPRIVATE=
set GOROOT=D:\Program Files\golang
set GOSUMDB=off
set GOTMPDIR=
set GOTOOLDIR=D:\Program Files\golang\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.16.3
set GCCGO=gccgo
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=C:\Users\STORYI~1\AppData\Local\Temp\go-build2449719716=/tmp/go-build -gno-record-gcc-switches

What did you do?

package main

import (
	"fmt"
	"time"
)

func main(){
	i := 0
	go func() {
		for {
			i++
		}
	}()
	ticker := time.NewTicker(time.Second)
	defer ticker.Stop()
	for {
		select {
		case <-ticker.C:
			fmt.Printf("i=%d \r\n", i)
		}
	}
}

What did you expect to see?

i should be increasing

What did you see instead?

i is always equal to 0

This seems like a very simple problem, but it doesn't meet intuitive expectations.

[davecheney]

Thank you for raising this issue, however this is not a bug, your program has a data race.

Have you tried running your program under the race detector? See https://blog.golang.org/race-detector .

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