DESCRIPTION ¶

Generate reproducible Go binaries.

Use asdf to manage Go versions.

COMMANDS ¶

Version Metadata ¶

Executables generated by the Go compiler can be byte for byte reproduced using metadata embedded in the binary. The metadata includes whether the version control has any local changes:

$ git clone https://github.com/msantos/goreap

$ cd goreap/cmd/goreap

$ git checkout 300f4137a4d9f90c4b41c7997e76a4a15bead740

$ CGO_ENABLED=0 go build -trimpath -ldflags "-s -w"

$ go version -m goreap
goreap: go1.18.1
        path    github.com/msantos/goreap/cmd/goreap
        mod     github.com/msantos/goreap       (devel)
        dep     golang.org/x/sys        v0.0.0-20210113181707-4bcb84eeeb78      h1:nVuTkr9L6Bq62qpUqKo/RnZCFfzDBL0bYo6w9OJUqZY=
        build   -compiler=gc
        build   -ldflags="-s -w"
        build   CGO_ENABLED=0
        build   GOARCH=amd64
        build   GOOS=linux
        build   GOAMD64=v1
        build   vcs=git
        build   vcs.revision=300f4137a4d9f90c4b41c7997e76a4a15bead740
        build   vcs.time=2022-04-17T12:29:28Z
        build   vcs.modified=false

$ sha256sum goreap
06780f56efac35dba2ff9ae105b94e97582e6164dc59abf8219c4fb24f11c27a  goreap

Unmanaged files in the git repository change the build metadata and the binary checksum:

$ touch foo

$ git status
...
Untracked files:
        foo

$ CGO_ENABLED=0 go build -trimpath -ldflags "-s -w"

$ go version -m goreap
goreap: go1.18.1
        path    github.com/msantos/goreap/cmd/goreap
        mod     github.com/msantos/goreap       (devel)
        dep     golang.org/x/sys        v0.0.0-20210113181707-4bcb84eeeb78      h1:nVuTkr9L6Bq62qpUqKo/RnZCFfzDBL0bYo6w9OJUqZY=
        build   -compiler=gc
        build   -ldflags="-s -w"
        build   CGO_ENABLED=0
        build   GOARCH=amd64
        build   GOOS=linux
        build   GOAMD64=v1
        build   vcs=git
        build   vcs.revision=300f4137a4d9f90c4b41c7997e76a4a15bead740
        build   vcs.time=2022-04-17T12:29:28Z
        build   vcs.modified=true

$ sha256sum goreap
162479ba1a84fa8a88bc9b72fe1e98bf3f2da565af0bbfb627f3baa1c2cb098c  goreap

Note:

vcs.modified is now set to true
the binary checksum differs
use a newly cloned or cleaned git repo before building

git clean -f -x -d

Compiling ¶

CGO_ENABLED=0 go build -trimpath -ldflags "-s -w"

CGO_ENABLED: disable use of libc, use pure go
-trimpath: remove paths from stacktraces
-ldflags: reduce binary size by removing debug tables

Versions ¶

Ensure the same Go version is installed:

asdf plugin add go https://github.com/asdf-community/asdf-golang.git
asdf install go $(asdf latest go)

The version for a git repo can be set:

$ asdf local go 1.17.5
$ git add .tool-versions

EXAMPLES ¶

Initialize Git Repository ¶

$ mkdir test
$ git init
$ curl --location https://raw.githubusercontent.com/github/gitignore/main/Go.gitignore > .gitignore

Create Go Modules ¶

$ go mod init test

main.go ¶

package main

import (
	"fmt"
	"os"
)

func main() {
	fmt.Fprintln(os.Stderr, "test")
}

Format and Run Linters ¶

$ go fmt ./...
$ golangci-lint run
$ golangci-lint run --enable-all

Commit Changes ¶

$ git add .
$ git commit

Compile for arm ¶

$ GOARCH=arm CGO_ENABLED=0 go build -trimpath -ldflags "-s -w"

Compare Hash ¶

# asdf install go 1.17.5
$ sha256sum test
7b85cb1914f6cdf34b58de83e0e52c30fcff7e8081824988c7db1c2572b4e0c4  test

(markdown)

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