Add go-version-file option (#62)

src/installer.ts

@@ -4,6 +4,7 @@ import * as path from 'path';
 import * as semver from 'semver';
 import * as httpm from '@actions/http-client';
 import * as sys from './system';
+import fs from 'fs';
 import os from 'os';
 
 type InstallationType = 'dist' | 'manifest';
@@ -298,3 +299,14 @@ export function makeSemver(version: string): string {
   }
   return fullVersion;
 }
+
+export function parseGoVersionFile(versionFilePath: string): string {
+  const contents = fs.readFileSync(versionFilePath).toString();
+
+  if (path.basename(versionFilePath) === 'go.mod') {
+    const match = contents.match(/^go (\d+(\.\d+)*)/m);
+    return match ? match[1] : '';
+  }
+
+  return contents.trim();
+}

src/main.ts

@@ -13,7 +13,7 @@ export async function run() {
     // versionSpec is optional.  If supplied, install / use from the tool cache
     // If not supplied then problem matchers will still be setup.  Useful for self-hosted.
     //
-    let versionSpec = core.getInput('go-version');
+    const versionSpec = resolveVersionInput();
 
     core.info(`Setup go version spec ${versionSpec}`);
 
@@ -104,3 +104,29 @@ export function parseGoVersion(versionString: string): string {
   // expecting go<version> for runtime.Version()
   return versionString.split(' ')[2].slice('go'.length);
 }
+
+function resolveVersionInput(): string {
+  let version = core.getInput('go-version');
+  const versionFilePath = core.getInput('go-version-file');
+
+  if (version && versionFilePath) {
+    core.warning(
+      'Both go-version and go-version-file inputs are specified, only go-version will be used'
+    );
+  }
+
+  if (version) {
+    return version;
+  }
+
+  if (versionFilePath) {
+    if (!fs.existsSync(versionFilePath)) {
+      throw new Error(
+        `The specified go version file at: ${versionFilePath} does not exist`
+      );
+    }
+    version = installer.parseGoVersionFile(versionFilePath);
+  }
+
+  return version;
+}