Modify README and action.yml per review

Signed-off-by: Steve Coffman <steve@khanacademy.org>

README.md

@@ -36,6 +36,7 @@ jobs:
     name: lint
     runs-on: ubuntu-latest
     steps:
+      - uses: actions/setup-go@v2
       - uses: actions/checkout@v2
       - name: golangci-lint
         uses: golangci/golangci-lint-action@v2
@@ -52,9 +53,6 @@ jobs:
           # Optional: show only new issues if it's a pull request. The default value is `false`.
           # only-new-issues: true
 
-          # Optional: if set to true then the action will use pre-installed Go.
-          # skip-go-installation: true
-
           # Optional: if set to true then the action don't cache or restore ~/go/pkg.
           # skip-pkg-cache: true
 
@@ -92,6 +90,7 @@ jobs:
     name: lint
     runs-on: ${{ matrix.os }}
     steps:
+      - uses: actions/setup-go@v2
       - uses: actions/checkout@v2
       - name: golangci-lint
         uses: golangci/golangci-lint-action@v2
@@ -133,7 +132,6 @@ The action was implemented with performance in mind:
 
 For example, in a repository of [golangci-lint](https://github.com/golangci/golangci-lint) running this action without the cache takes 50s, but with cache takes 14s:
   * in parallel:
-    * 13s to download Go
     * 4s to restore 50 MB of cache
     * 1s to find and install `golangci-lint`
   * 1s to run `golangci-lint` (it takes 35s without cache)

action.yml

@@ -20,10 +20,6 @@ inputs:
     description: "if set to true and the action runs on a pull request - the action outputs only newly found issues"
     default: false
     required: true
-  skip-go-installation:
-    description: "if set to true then action uses pre-installed Go"
-    default: false
-    required: true
   skip-pkg-cache:
     description: "if set to true then the action doesn't cache or restore ~/go/pkg."
     default: false