cmd/go: missing result of ReadBuildInfo in init function

[vearutop]

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

$ go1.12beta1 version
go version go1.12beta1 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

$ go1.12beta1 env
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/viacheslav.poturaev/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/viacheslav.poturaev/go"
GOPROXY=""
GORACE=""
GOROOT="/Users/viacheslav.poturaev/sdk/go1.12beta1"
GOTMPDIR=""
GOTOOLDIR="/Users/viacheslav.poturaev/sdk/go1.12beta1/pkg/tool/darwin_amd64"
GCCGO="gccgo"
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/lb/j0gz8jln36z4frqkrzmkdb0c0000gp/T/go-build125908091=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

I've tried to read build info in app retrieved with go get:

GO111MODULE=on go1.12beta1 get github.com/vearutop/go-versioning-example@v0.0.1
go: finding github.com/vearutop/go-versioning-example v0.0.1
go: finding go.uber.org/zap v1.3.0
go: finding go.uber.org/atomic v1.3.2

Then run ~/go/bin/go-versioning-example.
Here is a package to reproduce: https://github.com/vearutop/go-versioning-example

main package has two files: main.go and version.go. version.go has // +build go1.12 and init function that checks ReadBuildInfo.

What did you expect to see?

...some deps info...
2019-01-09T12:06:27.232+0100    INFO    go-versioning-example@v0.0.1/main.go:9    App Version: v0.0.1

What did you see instead?

build info not available
2019-01-09T12:06:27.232+0100    INFO    go-versioning-example@v0.0.1/main.go:9    App Version: dev

[vearutop]

If I change init() to init2() and call it explicitly from main() there is no issue.

[agnivade]

https://tip.golang.org/pkg/go/build/#hdr-Build_Constraints

There are no build tags for beta or minor releases.

I think this is what you are experiencing.

[vearutop]

As mentioned in slack #modules this is likely due to init execution precedence: https://golang.org/src/cmd/go/internal/modload/build.go#L234.

I've put my init code in a goroutine and now it works.

rm -rf ~/go/bin/go-versioning-example && GO111MODULE=on go1.12beta1 get github.com/vearutop/go-versioning-example@v0.0.2 && ~/go/bin/go-versioning-example
Build info: &{Path:github.com/vearutop/go-versioning-example Main:{Path:github.com/vearutop/go-versioning-example Version:v0.0.2 Sum:h1:KbExDVzJ29tWjzdV3PNHOX6o3f0fR0tnDR1zKNQ+Byg= Replace:<nil>} Deps:[0xc0000f0000 0xc0000f0040]}
2019-01-09T12:58:45.135+0100	INFO	go-versioning-example@v0.0.2/main.go:9	App Version: dev

[gopherbot]

Change https://golang.org/cl/157097 mentions this issue: cmd/go: remove init() to fix precedence issue when setting debug mod info

[gopherbot]

Change https://golang.org/cl/158357 mentions this issue: cmd/go/internal/modload: ensure that __debug_modinfo__ is not discarded during linking