fix:升级go mod

.github/workflows/build_test.yml

@@ -40,10 +40,10 @@ jobs:
     name: Backend build
     runs-on: ubuntu-latest
     steps:
-      - name: Set up Go 1.15
+      - name: Set up Go 1.6
         uses: actions/setup-go@v1
         with:
-          go-version: 1.15
+          go-version: 1.16
         id: go
 
       - name: Check out branch

server/go.mod

@@ -1,6 +1,6 @@
 module github.com/flipped-aurora/gin-vue-admin
 
-go 1.15
+go 1.16
 
 require (
 	github.com/StackExchange/wmi v0.0.0-20190523213315-cbe66965904d // indirect