update go version

Author: bajins

.github/workflows/upload-to-release.yml

@@ -25,7 +25,7 @@ jobs:
       - name: Install Go
         uses: actions/setup-go@v2
         with:
-          go-version: '^1.13.1'
+          go-version: '^1.15'
         id: go
 
       - name: Check out source code