Cannot speed compiling when using go build -mod=vendor

[jianzhangbjz]

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

$ go version
[cloud-user@preserve-olm-env ~]$ go version
go version go1.16.5 linux/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
[cloud-user@preserve-olm-env ~]$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN="/data/jian/go/bin"
GOCACHE="/home/cloud-user/.cache/go-build"
GOENV="/home/cloud-user/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/data/goproject/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/data/goproject"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/data/jian/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/data/jian/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.16.5"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build1279982106=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I want to use the dependency packages with specific versions, and don't want to depend on the Network. So, we use go build -mod=vendor for compiling. To save building time, we want to cache the binary so that it only rebuilds when the source is newer.

What did you expect to see?

When using go build for building, it saves the mod cache ( *.a files) to the $GOPATH/pkg/mod. We can reuse this cache and rebuilding the binary faster.
But, when using go build -mod=vendor, it works/saves the cache( *.a files) to a random temporary(such as /tmp/go-build1307922253/) WORK folder, and remove it once compiling done. So, that means, it will never reuse the mod cache when running go build -mod=vendor for compiling. Is it right?
So, how to utilize the mod cache to speed the compiling when using the go build -mod=vendor? Much appreciate!

What did you see instead?

[seankhliao]

Unlike many projects, the Go project does not use GitHub Issues for general discussion or asking questions. GitHub Issues are used for tracking bugs and proposals only.

For questions please refer to https://github.com/golang/go/wiki/Questions

[jianzhangbjz]

Thanks for your info, ask it in Slack: https://gophers.slack.com/archives/C029RQSEE/p1624784324040700

[jianzhangbjz]

Asked it again here: https://gophers.slack.com/archives/C9BMAAFFB/p1624841383206400

[jianzhangbjz]

Reopen it, since I thought this is a prroblem we should fix, at least a feature request.

[jianzhangbjz]

/reopen

[ianlancetaylor]

I don't think you are correctly describing how the system works. Please use a forum, as suggested above, to see how the system works, and then file an issue describing specific changes to make.

In particular the module cache, the build cache, and the temporary work directory are all different things.