fix:go version

.github/workflows/build_test.yml

@@ -40,10 +40,10 @@ jobs:
     name: Backend build
     runs-on: ubuntu-latest
     steps:
-      - name: Set up Go 1.14
+      - name: Set up Go 1.15
         uses: actions/setup-go@v1
         with:
-          go-version: 1.14
+          go-version: 1.15
         id: go
 
       - name: Check out branch