fix license-header gh action error (#3585)

Signed-off-by: Jari Kolehmainen <jari.kolehmainen@gmail.com>

.github/workflows/license-header.yml

@@ -14,6 +14,8 @@ jobs:
     - uses: actions/checkout@v2
     - name: Set up Golang
       uses: actions/setup-go@v2
+      with:
+        go-version: '^1.15.1'
     - name: Install addlicense
       run: |
         export PATH=${PATH}:`go env GOPATH`/bin