prefer globally installed bin

src/installer.ts

@@ -1,12 +1,9 @@
 import * as tc from '@actions/tool-cache';
-import * as cm from '@actions/core';
 import * as path from 'path';
 import * as semver from 'semver';
 import * as httpm from '@actions/http-client';
 import * as sys from './system';
 import {debug} from '@actions/core';
-import * as cp from 'child_process';
-import * as fs from 'fs';
 
 export async function downloadGo(
   versionSpec: string,
@@ -37,8 +34,6 @@ export async function downloadGo(
       // extracts with a root folder that matches the fileName downloaded
       const toolRoot = path.join(extPath, 'go');
       toolPath = await tc.cacheDir(toolRoot, 'go', makeSemver(match.version));
-
-      addBinToPath();
     }
   } catch (error) {
     throw new Error(`Failed to download version ${versionSpec}: ${error}`);
@@ -60,17 +55,6 @@ export interface IGoVersion {
   files: IGoVersionFile[];
 }
 
-export async function addBinToPath() {
-  let buf = cp.execSync('go env GOPATH');
-  if (buf) {
-    let d = buf.toString().trim();
-    let bp = path.join(d, 'bin');
-    if (fs.existsSync(bp)) {
-      cm.addPath(bp);
-    }
-  }
-}
-
 export async function findMatch(
   versionSpec: string,
   stable: boolean

src/main.ts

@@ -2,6 +2,8 @@ import * as core from '@actions/core';
 import * as tc from '@actions/tool-cache';
 import * as installer from './installer';
 import * as path from 'path';
+import * as cp from 'child_process';
+import * as fs from 'fs';
 
 export async function run() {
   try {
@@ -19,6 +21,8 @@ export async function run() {
       `Setup go ${stable ? 'stable' : ''} version spec ${versionSpec}`
     );
 
+    // if there's a globally install go and bin path, prefer that
+    let addedBin = addBinToPath();
     if (versionSpec) {
       let installDir: string | undefined = tc.find('go', versionSpec);
 
@@ -34,6 +38,12 @@ export async function run() {
         core.exportVariable('GOROOT', installDir);
         core.addPath(path.join(installDir, 'bin'));
         console.log('Added go to the path');
+
+        // if the global installed bin wasn't added,
+        // we can add the bin just installed
+        if (!addBinToPath) {
+          addBinToPath();
+        }
       } else {
         throw new Error(
           `Could not find a version that satisfied version spec: ${versionSpec}`
@@ -48,3 +58,17 @@ export async function run() {
     core.setFailed(error.message);
   }
 }
+
+function addBinToPath(): boolean {
+  let added = false;
+  let buf = cp.execSync('go env GOPATH');
+  if (buf) {
+    let d = buf.toString().trim();
+    let bp = path.join(d, 'bin');
+    if (fs.existsSync(bp)) {
+      core.addPath(bp);
+      added = true;
+    }
+  }
+  return added;
+}