Replace utility script with tasks

There is already a task for `go fmt` and `go vet`, so the remaining unique component of the `fmt_fix_vet`script was `go fix`.

Author: per1234

Diff for: .github/workflows/check-go.yml

@@ -39,6 +39,25 @@ jobs:
       - name: Check for errors
         run: task go:vet
 
+  check-outdated:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Install Task
+        uses: arduino/actions/setup-taskfile@master
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+          version: 3.x
+
+      - name: Modernize usages of outdated APIs
+        run: task go:fix
+
+      - name: Check if any fixes were needed
+        run: git diff --color --exit-code
+
   check-style:
     runs-on: ubuntu-latest
 

Diff for: Taskfile.yml

@@ -27,6 +27,11 @@ tasks:
     cmds:
       - go vet {{default .DEFAULT_GO_PACKAGES .GO_PACKAGES}}
 
+  go:fix:
+    desc: Modernize usages of outdated APIs
+    cmds:
+      - go fix {{default .DEFAULT_GO_PACKAGES .GO_PACKAGES}}
+
   go:lint:
     desc: Lint Go code
     cmds: