バージョンの埋め込みと表示

package main

var Version = "v1.2.3"

func main() {
    println(Version)
}

$ go build -ldflags="-X main.Version=v9.9.9" -o a.out

$ ./a.out
v9.9.9

$ go build -ldflags="-X main.Version=`git describe --tags`" -o a.out

builds:
-
  ldflags: -X main.Version=v{{ .Version }}

package main

import "runtime/debug"

var Version = ""

func replaceVersion(v string) string {
    if v != "" {
        return v
    }
    if info, ok := debug.ReadBuildInfo(); ok {
        if info.Main.Version != "" {
            return info.Main.Version
        }
        var revision, dirty string
        for _, v := range info.Settings {
            switch v.Key {
            case "vcs.revision":
                revision = v.Value
            case "vcs.modified":
                if v.Value == "true" {
                    dirty = "+dirty"
                }
            }
        }
        if revision != "" {
            return revision + dirty
        }
    }
    return "(version not set)"
}

func main() {
    println(replaceVersion(Version))
}

type BuildInfo struct {
    // GoVersion is the version of the Go toolchain that built the binary
    // (for example, "go1.19.2").
    GoVersion string `json:",omitempty"`

    // Path is the package path of the main package for the binary
    // (for example, "golang.org/x/tools/cmd/stringer").
    Path string `json:",omitempty"`

    // Main describes the module that contains the main package for the binary.
    Main Module `json:""`

    // Deps describes all the dependency modules, both direct and indirect,
    // that contributed packages to the build of this binary.
    Deps []*Module `json:",omitempty"`

    // Settings describes the build settings used to build the binary.
    Settings []BuildSetting `json:",omitempty"`
}

type Module struct {
    Path    string  `json:",omitempty"` // module path
    Version string  `json:",omitempty"` // module version
    Sum     string  `json:",omitempty"` // checksum
    Replace *Module `json:",omitempty"` // replaced by this module
}

$ go build -o a.out && ./a.out
(devel)

type BuildSetting struct {
    // Key and Value describe the build setting.
    // Key must not contain an equals sign, space, tab, or newline.
    Key string `json:",omitempty"`
    // Value must not contain newlines ('\n').
    Value string `json:",omitempty"`
}

$ go run main.go
(version not set)