Update actions/checkout action to v2

.github/workflows/go-test.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-20.04
 
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
     - uses: actions/setup-go@v2.1.4
       with:
         go-version: '1.16'

.github/workflows/jshint.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-20.04
 
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
 
     - name: apt
       run: sudo apt-get install -y nodejs npm

.github/workflows/release.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-20.04
 
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2
 
     - name: build
       run: make release