GitHub: revert to latest runner version, fix cache

With this we revert back to the latest ubuntu runner for the postgres
itest. We also optimize the cache by also including the build cache, not
just the module cache.

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

@@ -8,7 +8,12 @@ runs:
     - name: Query cache for go artifacts
       uses: actions/cache@v3
       with:
-        path: /home/runner/work/go
+        # In order:
+        # * Module download cache
+        # * Build cache (Linux)
+        path: |
+          ~/go/pkg/mod
+          ~/.cache/go-build
         key: taproot-assets-${{ runner.os }}-go-${{ env.GO_VERSION }}-${{ github.job }}-${{ hashFiles('**/go.sum') }}
         restore-keys: |
           taproot-assets-${{ runner.os }}-go-${{ env.GO_VERSION }}-${{ github.job }}-${{ hashFiles('**/go.sum') }}

.github/workflows/main.yaml

@@ -17,10 +17,7 @@ defaults:
 
 env:
   # go needs absolute directories, using the $HOME variable doesn't work here.
-  GOCACHE: /home/runner/work/go/pkg/build
-  GOMODCACHE: /home/runner/work/go/pkg/mod
   GOPATH: /home/runner/work/go
-  GO111MODULE: on
 
   # If you change this value, please change it in the following files as well:
   # /Dockerfile
@@ -236,7 +233,7 @@ jobs:
   ########################
   integration-test-postgres:
     name: run itests postgres
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
       - name: git checkout
         uses: actions/checkout@v3