.github: Bump actions/setup-go from v1 to v2.1.3 (#21)

Bumps [actions/setup-go](https://github.com/actions/setup-go) from v1 to v2.
- [Release notes](https://github.com/actions/setup-go/releases)
- [Commits](actions/setup-go@v1...37335c7)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Ross Light <ross@zombiezen.com>

.github/workflows/build.yml

@@ -43,7 +43,7 @@ jobs:
           libz-dev \
           xz-utils
     - name: Set up Go
-      uses: actions/setup-go@v1
+      uses: actions/setup-go@v2
       with:
         go-version: 1.15
     - name: Check out code
@@ -71,7 +71,7 @@ jobs:
     - name: Install xz
       run: brew update && brew install xz
     - name: Set up Go
-      uses: actions/setup-go@v1
+      uses: actions/setup-go@v2
       with:
         go-version: 1.15
     - name: Check out code
@@ -97,7 +97,7 @@ jobs:
     runs-on: windows-latest
     steps:
     - name: Set up Go
-      uses: actions/setup-go@v1
+      uses: actions/setup-go@v2
       with:
         go-version: 1.15
     - name: Check out code

.github/workflows/publish.yml

@@ -24,7 +24,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Set up Go
-      uses: actions/setup-go@v1
+      uses: actions/setup-go@v2
       with:
         go-version: 1.15
     - name: Fetch release from proxy