Install golangci-lint as a separate step

In order to avoid the directory changing shenanigans. Also use a custom
Go version instead of the system provided one.

.github/workflows/all.yml

@@ -43,13 +43,15 @@ jobs:
         uses: actions/checkout@v2
         with:
           fetch-depth: 0
-      - name: Lint
+      - name: Install Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: 1.14.x
+      - name: Install golangci-lint
+        working-directory: /tmp
+        run: go get github.com/golangci/golangci-lint/cmd/golangci-lint@$GOLANGCI_VERSION
+      - name: Run linters
         run: |
-          pushd .
-          cd $(mktemp -d)
-          go get github.com/golangci/golangci-lint/cmd/golangci-lint@$GOLANGCI_VERSION
-          export PATH="$HOME/go/bin:$PATH"
-          popd
           BASEREV=$(git merge-base HEAD origin/master)
           echo "Base revision: $BASEREV"
           golangci-lint run --out-format=tab --new-from-rev "$BASEREV" ./...