feat: add support for reading golangci-lint version from go.mod

Implements automatic version detection from go.mod files to keep
golangci-lint versions synchronized between the module and CI.

- Add new `go-mod-path` input parameter to specify custom go.mod location
- Automatically detect and use version from go.mod when no explicit version provided
- Force `goinstall` mode when using go.mod versions for compatibility
- Support both default go.mod and custom paths (e.g., tools/go.mod)

This eliminates the need to manually update versions in multiple places
and ensures CI uses the same golangci-lint version as the project.

Fixes #1268

Signed-off-by: Pedro Tanaka <pedro.tanaka@shopify.com>

README.md

@@ -105,6 +105,68 @@ You will also likely need to add the following `.gitattributes` file to ensure t
 
 </details>
 
+<details>
+<summary>Using go.mod Version Example</summary>
+
+If you have golangci-lint as a dependency in your go.mod file, you can use that version automatically:
+
+```yaml
+name: golangci-lint
+on:
+  push:
+    branches:
+      - main
+      - master
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  golangci:
+    name: lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version: stable
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v8
+        # No version specified - will read from go.mod automatically
+```
+
+Or if you have a separate tools module:
+
+```yaml
+name: golangci-lint
+on:
+  push:
+    branches:
+      - main
+      - master
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  golangci:
+    name: lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version: stable
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v8
+        with:
+          go-mod-path: tools/go.mod
+```
+
+</details>
+
 <details>
 <summary>Go Workspace Example</summary>
 
@@ -280,6 +342,29 @@ with:
 
 </details>
 
+### `go-mod-path`
+
+(optional)
+
+Path to a go.mod file to read the golangci-lint version from.
+If specified and `version` is not set, the action will parse the go.mod file to determine the golangci-lint version.
+
+Default is "go.mod" in the working directory.
+
+**Note:** When a version is read from go.mod, it automatically uses `goinstall` install-mode to ensure compatibility with your module's dependencies.
+
+<details>
+<summary>Example</summary>
+
+```yml
+uses: golangci/golangci-lint-action@v8
+with:
+  go-mod-path: tools/go.mod
+  # ...
+```
+
+</details>
+
 ### `install-mode`
 
 (optional)
@@ -288,6 +373,8 @@ The mode to install golangci-lint: it can be `binary`, `goinstall`, or `none`.
 
 The default value is `binary`.
 
+**Note:** When using `go-mod-path` to read the version from a go.mod file, the install-mode is automatically set to `goinstall`.
+
 <details>
 <summary>Example</summary>
 

action.yml

@@ -11,6 +11,13 @@ inputs:
       - `goinstall`: the value can be v2.3.4, `latest`, or the hash of a commit.
       - `none`: the value is ignored.
     required: false
+  go-mod-path:
+    description: |
+      Path to a go.mod file to read the golangci-lint version from.
+      If specified and version is not set, the action will parse the go.mod file
+      to determine the golangci-lint version. Default is "go.mod" in the working directory.
+      Note: When a version is read from go.mod, it automatically uses `goinstall` install-mode.
+    required: false
   install-mode:
     description: "The mode to install golangci-lint. It can be 'binary', 'goinstall', or 'none'."
     default: "binary"

dist/post_run/index.js

@@ -92671,7 +92671,7 @@ const printOutput = (res) => {
  * @returns             path to installed binary of golangci-lint.
  */
 async function install() {
-    const mode = core.getInput("install-mode").toLowerCase();
+    let mode = core.getInput("install-mode").toLowerCase();
     if (mode === InstallMode.None) {
         const binPath = await (0, which_1.default)("golangci-lint", { nothrow: true });
         if (!binPath) {
@@ -92679,6 +92679,11 @@ async function install() {
         }
         return binPath;
     }
+    // If version is being read from go.mod, force goinstall mode
+    if ((0, version_1.isVersionFromGoMod)()) {
+        core.info(`Version detected from go.mod file, using goinstall mode`);
+        mode = InstallMode.GoInstall;
+    }
     const versionInfo = await (0, version_1.getVersion)(mode);
     return await installBinary(versionInfo, mode);
 }
@@ -93358,6 +93363,7 @@ var __importDefault = (this && this.__importDefault) || function (mod) {
 };
 Object.defineProperty(exports, "__esModule", ({ value: true }));
 exports.stringifyVersion = void 0;
+exports.isVersionFromGoMod = isVersionFromGoMod;
 exports.getVersion = getVersion;
 const core = __importStar(__nccwpck_require__(7484));
 const httpm = __importStar(__nccwpck_require__(4844));
@@ -93412,8 +93418,9 @@ const isLessVersion = (a, b) => {
 const getRequestedVersion = () => {
     let requestedVersion = core.getInput(`version`);
     const workingDirectory = core.getInput(`working-directory`);
-    let goMod = "go.mod";
+    const goModPath = core.getInput(`go-mod-path`);
-    if (workingDirectory) {
+    let goMod = goModPath || "go.mod";
+    if (!path_1.default.isAbsolute(goMod) && workingDirectory) {
         goMod = path_1.default.join(workingDirectory, goMod);
     }
     if (requestedVersion == "" && fs.existsSync(goMod)) {
@@ -93451,10 +93458,27 @@ const fetchVersionMapping = async () => {
         throw new Error(`failed to get action config: ${exc.message}`);
     }
 };
+function isVersionFromGoMod() {
+    const requestedVersion = core.getInput(`version`);
+    const goModPath = core.getInput(`go-mod-path`);
+    const workingDirectory = core.getInput(`working-directory`);
+    let goMod = goModPath || "go.mod";
+    if (!path_1.default.isAbsolute(goMod) && workingDirectory) {
+        goMod = path_1.default.join(workingDirectory, goMod);
+    }
+    return requestedVersion == "" && fs.existsSync(goMod);
+}
 async function getVersion(mode) {
     core.info(`Finding needed golangci-lint version...`);
     if (mode == install_1.InstallMode.GoInstall) {
-        const v = core.getInput(`version`);
+        let v = core.getInput(`version`);
+        // If no explicit version is provided, check go.mod
+        if (!v && isVersionFromGoMod()) {
+            const reqVersion = getRequestedVersion();
+            if (reqVersion) {
+                v = (0, exports.stringifyVersion)(reqVersion);
+            }
+        }
         return { TargetVersion: v ? v : "latest" };
     }
     const reqVersion = getRequestedVersion();

dist/run/index.js

@@ -92671,7 +92671,7 @@ const printOutput = (res) => {
  * @returns             path to installed binary of golangci-lint.
  */
 async function install() {
-    const mode = core.getInput("install-mode").toLowerCase();
+    let mode = core.getInput("install-mode").toLowerCase();
     if (mode === InstallMode.None) {
         const binPath = await (0, which_1.default)("golangci-lint", { nothrow: true });
         if (!binPath) {
@@ -92679,6 +92679,11 @@ async function install() {
         }
         return binPath;
     }
+    // If version is being read from go.mod, force goinstall mode
+    if ((0, version_1.isVersionFromGoMod)()) {
+        core.info(`Version detected from go.mod file, using goinstall mode`);
+        mode = InstallMode.GoInstall;
+    }
     const versionInfo = await (0, version_1.getVersion)(mode);
     return await installBinary(versionInfo, mode);
 }
@@ -93358,6 +93363,7 @@ var __importDefault = (this && this.__importDefault) || function (mod) {
 };
 Object.defineProperty(exports, "__esModule", ({ value: true }));
 exports.stringifyVersion = void 0;
+exports.isVersionFromGoMod = isVersionFromGoMod;
 exports.getVersion = getVersion;
 const core = __importStar(__nccwpck_require__(7484));
 const httpm = __importStar(__nccwpck_require__(4844));
@@ -93412,8 +93418,9 @@ const isLessVersion = (a, b) => {
 const getRequestedVersion = () => {
     let requestedVersion = core.getInput(`version`);
     const workingDirectory = core.getInput(`working-directory`);
-    let goMod = "go.mod";
+    const goModPath = core.getInput(`go-mod-path`);
-    if (workingDirectory) {
+    let goMod = goModPath || "go.mod";
+    if (!path_1.default.isAbsolute(goMod) && workingDirectory) {
         goMod = path_1.default.join(workingDirectory, goMod);
     }
     if (requestedVersion == "" && fs.existsSync(goMod)) {
@@ -93451,10 +93458,27 @@ const fetchVersionMapping = async () => {
         throw new Error(`failed to get action config: ${exc.message}`);
     }
 };
+function isVersionFromGoMod() {
+    const requestedVersion = core.getInput(`version`);
+    const goModPath = core.getInput(`go-mod-path`);
+    const workingDirectory = core.getInput(`working-directory`);
+    let goMod = goModPath || "go.mod";
+    if (!path_1.default.isAbsolute(goMod) && workingDirectory) {
+        goMod = path_1.default.join(workingDirectory, goMod);
+    }
+    return requestedVersion == "" && fs.existsSync(goMod);
+}
 async function getVersion(mode) {
     core.info(`Finding needed golangci-lint version...`);
     if (mode == install_1.InstallMode.GoInstall) {
-        const v = core.getInput(`version`);
+        let v = core.getInput(`version`);
+        // If no explicit version is provided, check go.mod
+        if (!v && isVersionFromGoMod()) {
+            const reqVersion = getRequestedVersion();
+            if (reqVersion) {
+                v = (0, exports.stringifyVersion)(reqVersion);
+            }
+        }
         return { TargetVersion: v ? v : "latest" };
     }
     const reqVersion = getRequestedVersion();

src/install.ts

@@ -6,7 +6,7 @@ import path from "path"
 import { promisify } from "util"
 import which from "which"
 
-import { getVersion, VersionInfo } from "./version"
+import { getVersion, isVersionFromGoMod, VersionInfo } from "./version"
 
 const execShellCommand = promisify(exec)
 
@@ -36,7 +36,7 @@ const printOutput = (res: ExecRes): void => {
  * @returns             path to installed binary of golangci-lint.
  */
 export async function install(): Promise<string> {
-  const mode = core.getInput("install-mode").toLowerCase()
+  let mode = core.getInput("install-mode").toLowerCase()
 
   if (mode === InstallMode.None) {
     const binPath = await which("golangci-lint", { nothrow: true })
@@ -46,6 +46,12 @@ export async function install(): Promise<string> {
     return binPath
   }
 
+  // If version is being read from go.mod, force goinstall mode
+  if (isVersionFromGoMod()) {
+    core.info(`Version detected from go.mod file, using goinstall mode`)
+    mode = InstallMode.GoInstall
+  }
+
   const versionInfo = await getVersion(<InstallMode>mode)
 
   return await installBinary(versionInfo, <InstallMode>mode)

src/version.ts

@@ -68,9 +68,10 @@ const isLessVersion = (a: Version, b: Version): boolean => {
 const getRequestedVersion = (): Version => {
   let requestedVersion = core.getInput(`version`)
   const workingDirectory = core.getInput(`working-directory`)
+  const goModPath = core.getInput(`go-mod-path`)
 
-  let goMod = "go.mod"
+  let goMod = goModPath || "go.mod"
-  if (workingDirectory) {
+  if (!path.isAbsolute(goMod) && workingDirectory) {
     goMod = path.join(workingDirectory, goMod)
   }
 
@@ -129,11 +130,32 @@ const fetchVersionMapping = async (): Promise<VersionMapping> => {
   }
 }
 
+export function isVersionFromGoMod(): boolean {
+  const requestedVersion = core.getInput(`version`)
+  const goModPath = core.getInput(`go-mod-path`)
+  const workingDirectory = core.getInput(`working-directory`)
+
+  let goMod = goModPath || "go.mod"
+  if (!path.isAbsolute(goMod) && workingDirectory) {
+    goMod = path.join(workingDirectory, goMod)
+  }
+
+  return requestedVersion == "" && fs.existsSync(goMod)
+}
+
 export async function getVersion(mode: InstallMode): Promise<VersionInfo> {
   core.info(`Finding needed golangci-lint version...`)
 
   if (mode == InstallMode.GoInstall) {
-    const v: string = core.getInput(`version`)
+    let v: string = core.getInput(`version`)
+
+    // If no explicit version is provided, check go.mod
+    if (!v && isVersionFromGoMod()) {
+      const reqVersion = getRequestedVersion()
+      if (reqVersion) {
+        v = stringifyVersion(reqVersion)
+      }
+    }
 
     return { TargetVersion: v ? v : "latest" }
   }