Use go 1.20 (#122)

.github/workflows/flutterfmt.yml

@@ -16,12 +16,12 @@ jobs:
     steps:
 
       - name: Install flutter
-        uses: subosito/flutter-action@v1
+        uses: subosito/flutter-action@v2
         with:
           flutter-version: '3.3.5'
 
       - name: Check out code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: flutter format
         run: $GITHUB_WORKSPACE/.github/workflows/flutterfmt.sh

.github/workflows/gofmt.yml

@@ -15,14 +15,14 @@ jobs:
     runs-on: ubuntu-latest
     steps:
 
-      - name: Set up Go 1.16
-        uses: actions/setup-go@v2
+      - name: Set up Go 1.20
+        uses: actions/setup-go@v4
         with:
-          go-version: 1.16
+          go-version: "1.20"
         id: go
 
       - name: Check out code into the Go module directory
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Install goimports
         working-directory: nebula

.github/workflows/release.yml

@@ -11,10 +11,10 @@ jobs:
     runs-on: macos-latest
 
     steps:
-      - name: Set up Go 1.19.1
-        uses: actions/setup-go@v2
+      - name: Set up Go 1.20
+        uses: actions/setup-go@v4
         with:
-          go-version: 1.19.1
+          go-version: "1.20"
 
       - uses: actions/setup-java@v2
         with: