Add Go toolchain detection

src/detect.js

@@ -61,6 +61,24 @@ async function detectPyproject(root, output) {
     if (match) add(output, "python", "pyproject.toml", match[1], index + 1);
   }
 }
+async function detectGoMod(root, output) {
+  const content = await read(root, "go.mod");
+  if (!content) return;
+
+  const lines = content.split(/\r?\n/);
+
+  for (const [index, line] of lines.entries()) {
+    const go = line.match(/^\s*go\s+(\S+)/);
+    if (go) {
+      add(output, "go", "go.mod", go[1], index + 1);
+    }
+
+    const toolchain = line.match(/^\s*toolchain\s+go(\S+)/);
+    if (toolchain) {
+      add(output, "go", "go.mod", toolchain[1], index + 1);
+    }
+  }
+}
 
 async function detectToolVersions(root, output) {
   const content = await read(root, ".tool-versions");
@@ -96,8 +114,17 @@ async function detectDockerfiles(root, output) {
     if (!entry.isFile() || !/^Dockerfile(?:\..+)?$/i.test(entry.name)) continue;
     const content = await read(root, entry.name);
     for (const [index, line] of content.split(/\r?\n/).entries()) {
-      const match = line.match(/^\s*FROM\s+(?:[^/\s]+\/)?(node|python):([^\s@]+)/i);
-      if (match) add(output, match[1].toLowerCase(), entry.name, match[2], index + 1);
+      const match = line.match(
+        /^\s*FROM\s+(?:[^/\s]+\/)?(node|python|golang):([^\s@]+)/i,
+      );
+      if (match)
+        add(
+          output,
+          match[1].toLowerCase() === "golang" ? "go" : match[1].toLowerCase(),
+          entry.name,
+          match[2],
+          index + 1,
+        );
     }
   }
 }
@@ -124,7 +151,7 @@ async function detectGithubActions(root, output) {
     let remaining = 0;
 
     for (const [index, line] of lines.entries()) {
-      const action = line.match(/uses:\s*actions\/setup-(node|python)@/i);
+      const action = line.match(/uses:\s*actions\/setup-(node|python|go)@/i);
       if (action) {
         runtime = action[1].toLowerCase();
         remaining = 12;
@@ -135,7 +162,7 @@ async function detectGithubActions(root, output) {
         continue;
       }
       remaining -= 1;
-      const declared = line.match(/(?:node-version|python-version):\s*["']?([^"'#\s]+)/i);
+      const declared = line.match(/(?:node-version|python-version|go-version):\s*["']?([^"'#\s]+)/i);
       if (runtime && declared && !declared[1].startsWith("${{")) {
         add(output, runtime, file, declared[1], index + 1);
         runtime = null;
@@ -150,6 +177,7 @@ export async function detectDeclarations(root) {
     detectVersionFiles(root, output),
     detectPackageJson(root, output),
     detectPyproject(root, output),
+    detectGoMod(root, output),
     detectToolVersions(root, output),
     detectMise(root, output),
     detectDockerfiles(root, output),

src/format.js

@@ -2,6 +2,12 @@ function location(declaration) {
   return declaration.line ? `${declaration.file}:${declaration.line}` : declaration.file;
 }
 
+const LABELS = {
+  go: "Go",
+  node: "Node.js",
+  python: "Python",
+};
+
 export function formatHuman(result) {
   if (result.runtimes.length === 0) {
     return "No supported runtime declarations found.";
@@ -14,7 +20,7 @@ export function formatHuman(result) {
     });
 
     if (!runtime.ok) {
-      const label = runtime.runtime === "node" ? "Node.js" : "Python";
+      const label = LABELS[runtime.runtime] ?? runtime.runtime;
       rows.push("", `  No ${label} version satisfies every declaration.`);
     } else if (runtime.declarations.some((declaration) => !declaration.parsed)) {
       rows.push("", "  Some declarations could not be parsed.");

test/detect.test.js

@@ -12,17 +12,24 @@ test("finds aligned Node.js and Python declarations", async () => {
   assert.equal(result.ok, true);
   assert.deepEqual(
     result.runtimes.map((runtime) => runtime.runtime),
-    ["node", "python"],
+    ["go", "node", "python"],
   );
-  assert.equal(result.runtimes[0].declarations.length, 5);
+  assert.equal(result.runtimes[0].declarations.length, 3);
   assert.equal(result.runtimes[1].declarations.length, 5);
+  assert.equal(result.runtimes[2].declarations.length, 5);
 });
 
 test("finds Docker and project-file drift", async () => {
   const result = await inspect(path.join(here, "fixtures", "drift"));
-
   assert.equal(result.ok, false);
-  assert.equal(result.runtimes[0].runtime, "node");
+  assert.deepEqual(
+    result.runtimes.map((runtime) => runtime.runtime),
+    ["go", "node"],
+  );
+  const go = result.runtimes.find((runtime) => runtime.runtime === "go");
+
+  assert.ok(go);
+  assert.equal(go.ok, false);
 });
 
 test("returns an empty success for a directory with no declarations", async () => {

test/fixtures/aligned/.github/workflows/ci.yml

@@ -9,3 +9,8 @@ jobs:
       - uses: actions/setup-python@v5
         with:
           python-version: "3.12"
+  go:
+    steps:
+      - uses: actions/setup-go@v5
+        with:
+          go-version: "1.24"

test/fixtures/aligned/go.mod

@@ -0,0 +1,2 @@
+go 1.24
+toolchain go1.24.3

test/fixtures/drift/Dockerfile

@@ -1 +1,2 @@
 FROM node:20-alpine
+FROM golang:1.23

test/fixtures/drift/go.mod

@@ -0,0 +1 @@
+go 1.24