go/analysis: expose GoMod to Pass.Module

go.mod (w/ go.sum in the same dir) is needed by
https://github.com/AkihiroSuda/gosocialcheck
to check the reputation of dependencies.

Fixes golang/go#73878

Signed-off-by: Akihiro Suda <[email protected]>

Author: AkihiroSuda

go/analysis/analysis.go

@@ -252,5 +252,6 @@ type Fact interface {
 type Module struct {
 	Path      string // module path
 	Version   string // module version ("" if unknown, such as for workspace modules)
+	GoMod     string // path to go.mod file used when loading this module, if any
 	GoVersion string // go version used in module (e.g. "go1.22.0")
 }

go/analysis/checker/checker.go

@@ -321,6 +321,7 @@ func (act *Action) execOnce() {
 	if mod := act.Package.Module; mod != nil {
 		module.Path = mod.Path
 		module.Version = mod.Version
+		module.GoMod = mod.GoMod
 		module.GoVersion = mod.GoVersion
 	}