Fix install-go cache key

Signed-off-by: Brad Davidson <brad.davidson@rancher.com>

Author: brandond

.github/actions/setup-go/action.yaml

@@ -8,6 +8,14 @@ inputs:
 runs:
   using: 'composite'
   steps:
+    # On self-hosted runners, the env.ImageOS variable may not be set correctly, which can cause issues with the cache key.
+    # We need to handle this case to ensure the cache key is consistent.
+    - name: Set ImageOS
+      if: ${{ runner.os == 'Linux' && env.ImageOS == '' }}
+      shell: bash
+      # Key is ubuntu<MAJOR>, as there is not other linux os in GHA other than Ubuntu
+      run: echo "ImageOS=ubuntu$(lsb_release -rs | cut -d. -f1)" >> $GITHUB_ENV
+
     - name: Find Latest Release Branch
       shell: bash
       run: |
@@ -41,4 +49,4 @@ runs:
         # Match the cache key to the setup-go action https://github.com/actions/setup-go/blob/main/src/cache-restore.ts#L34
         key: setup-go-${{ runner.os }}-${{ env.ImageOS }}-go-${{ env.GO_VERSION }}-${{ hashFiles('go.sum') }}
         restore-keys: |
-          setup-go-${{ runner.os }}-
+          setup-go-${{ runner.os }}-${{ env.ImageOS }}-go-${{ env.GO_VERSION }}-