go/src/main.ts

import * as core from '@actions/core';
import * as tc from '@actions/tool-cache';
import * as installer from './installer';
import * as path from 'path';

export async function run() {
  try {
    //
    // 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');
    
    // stable will be true unless false is the exact input
    // since getting unstable versions should be explicit
    let stable = Boolean(core.getInput('stable') || 'true');

    if (versionSpec) {
      let installDir: string | undefined = tc.find('go', versionSpec);

      if (!installDir) {
        installDir = await installer.downloadGo(versionSpec, stable);
      }

      if (installDir) {
        core.exportVariable('GOROOT', installDir);
        core.addPath(path.join(installDir, 'bin'));
      } else {
        throw new Error(
          `Could not find a version that satisfied version spec: ${versionSpec}`
        );
      }
    }

    // add problem matchers
    const matchersPath = path.join(__dirname, '..', 'matchers.json');
    console.log(`##[add-matcher]${matchersPath}`);
  } catch (error) {
    core.setFailed(error.message);
  }
}