Bump actions/checkout from v1 to v2.3.4

Bumps [actions/checkout](https://github.com/actions/checkout) from v1 to v2.3.4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v1...5a4ac90)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/main.yml

@@ -15,7 +15,7 @@ jobs:
         go-version: ${{ matrix.go }}
 
     - name: Check out code into the Go module directory
-      uses: actions/checkout@v1
+      uses: actions/checkout@v2.3.4
 
     - name: Download dependencies
       run: go mod download