[autoroll] Use golang.FindGo in GoModParent, make test non-manual

Bug: skia:13827
Change-Id: I21e740e2978febb1a47c930adbad2ca8b8e9bc79
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/596057
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Auto-Submit: Eric Boren <borenet@google.com>
diff --git a/autoroll/go/repo_manager/parent/BUILD.bazel b/autoroll/go/repo_manager/parent/BUILD.bazel
index 9b46fb8..c51d82d 100644
--- a/autoroll/go/repo_manager/parent/BUILD.bazel
+++ b/autoroll/go/repo_manager/parent/BUILD.bazel
@@ -41,6 +41,7 @@
         "//go/git/git_common",
         "//go/github",
         "//go/go_install",
+        "//go/golang",
         "//go/metrics2",
         "//go/skerr",
         "//go/sklog",
@@ -56,7 +57,7 @@
     name = "parent_test",
     srcs = [
         "gitiles_test.go",
-        "go_mod_manual_test.go",
+        "go_mod_test.go",
         "pre_upload_steps_test.go",
     ],
     embed = [":parent"],
diff --git a/autoroll/go/repo_manager/parent/go_mod.go b/autoroll/go/repo_manager/parent/go_mod.go
index 4352193..57cb252 100644
--- a/autoroll/go/repo_manager/parent/go_mod.go
+++ b/autoroll/go/repo_manager/parent/go_mod.go
@@ -19,6 +19,7 @@
 	"go.skia.org/infra/go/exec"
 	"go.skia.org/infra/go/gerrit"
 	"go.skia.org/infra/go/git"
+	"go.skia.org/infra/go/golang"
 	"go.skia.org/infra/go/skerr"
 	"go.skia.org/infra/go/sklog"
 )
@@ -77,12 +78,17 @@
 		return nil, skerr.Wrap(err)
 	}
 
+	goBin, err := golang.FindGo()
+	if err != nil {
+		return nil, skerr.Wrap(err)
+	}
+
 	createRoll := func(ctx context.Context, co *git.Checkout, from *revision.Revision, to *revision.Revision, rolling []*revision.Revision, commitMsg string) (string, error) {
 		// Update the Go module.
-		if _, err := exec.RunCwd(ctx, co.Dir(), "go", "get", fmt.Sprintf("%s@%s", c.ModulePath, to.Id)); err != nil {
+		if _, err := exec.RunCwd(ctx, co.Dir(), goBin, "get", fmt.Sprintf("%s@%s", c.ModulePath, to.Id)); err != nil {
 			return "", skerr.Wrap(err)
 		}
-		if _, err := exec.RunCwd(ctx, co.Dir(), "go", "mod", "tidy"); err != nil {
+		if _, err := exec.RunCwd(ctx, co.Dir(), goBin, "mod", "tidy"); err != nil {
 			return "", skerr.Wrap(err)
 		}
 
diff --git a/autoroll/go/repo_manager/parent/go_mod_manual_test.go b/autoroll/go/repo_manager/parent/go_mod_test.go
similarity index 100%
rename from autoroll/go/repo_manager/parent/go_mod_manual_test.go
rename to autoroll/go/repo_manager/parent/go_mod_test.go