Upgrade go to go 1.15

Signed-off-by: Wesley Pettit <[email protected]>

.github/workflows/build.yml

@@ -13,17 +13,17 @@ jobs:
     runs-on: ubuntu-latest
     steps:
 
-    - name: Set up Go 1.12
+    - name: Set up Go 1.15
       uses: actions/setup-go@v2
       with:
-        go-version: 1.12
+        go-version: 1.15
       id: go
 
     - name: Check out code into the Go module directory
       uses: actions/checkout@v2
-      
+
     - name: golint
       run: go get -u golang.org/x/lint/golint
- 
+
     - name: Build
       run: make build test