Implement "check-latest" flag to check if pre-cached version is latest one (#186)

src/installer.ts

@@ -31,11 +31,27 @@ export interface IGoVersionInfo {
 export async function getGo(
   versionSpec: string,
   stable: boolean,
+  checkLatest: boolean,
   auth: string | undefined
 ) {
   let osPlat: string = os.platform();
   let osArch: string = os.arch();
 
+  if (checkLatest) {
+    core.info('Attempting to resolve the latest version from the manifest...');
+    const resolvedVersion = await resolveVersionFromManifest(
+      versionSpec,
+      stable,
+      auth
+    );
+    if (resolvedVersion) {
+      versionSpec = resolvedVersion;
+      core.info(`Resolved as '${versionSpec}'`);
+    } else {
+      core.info(`Failed to resolve version ${versionSpec} from manifest`);
+    }
+  }
+
   // check cache
   let toolPath: string;
   toolPath = tc.find('go', versionSpec);
@@ -97,6 +113,20 @@ export async function getGo(
   return downloadPath;
 }
 
+async function resolveVersionFromManifest(
+  versionSpec: string,
+  stable: boolean,
+  auth: string | undefined
+): Promise<string | undefined> {
+  try {
+    const info = await getInfoFromManifest(versionSpec, stable, auth);
+    return info?.resolvedVersion;
+  } catch (err) {
+    core.info('Unable to resolve a version from the manifest...');
+    core.debug(err.message);
+  }
+}
+
 async function installGoVersion(
   info: IGoVersionInfo,
   auth: string | undefined

src/main.ts

@@ -24,7 +24,13 @@ export async function run() {
       let token = core.getInput('token');
       let auth = !token || isGhes() ? undefined : `token ${token}`;
 
-      const installDir = await installer.getGo(versionSpec, stable, auth);
+      const checkLatest = core.getBooleanInput('check-latest');
+      const installDir = await installer.getGo(
+        versionSpec,
+        stable,
+        checkLatest,
+        auth
+      );
 
       core.exportVariable('GOROOT', installDir);
       core.addPath(path.join(installDir, 'bin'));