chore: update runner to ubuntu-latest

.github/workflows/build.yml

@@ -5,7 +5,7 @@ on: workflow_dispatch
 jobs:
   build:
     name: Build
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - name: Set up Go 1.20
         uses: actions/setup-go@v2

.github/workflows/test.yml

@@ -10,12 +10,12 @@ on:
 jobs:
   test:
     name: Test
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
-      - name: Set up Go 1.18
+      - name: Set up Go 1.20
         uses: actions/setup-go@v2
         with:
-          go-version: "1.18"
+          go-version: "1.20"
         id: go
 
       - name: Check out code into the Go module directory