update go.yml and travis.yml to go1.15

.github/workflows/go.yml

@@ -10,10 +10,10 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     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 code into the Go module directory

.travis.yml

@@ -12,7 +12,8 @@ go:
   # - 1.11.x
   # - 1.12.x
   # - 1.13.x
-  - 1.14.x
+  # - 1.14.x
+  - 1.15.x
   # - tip
 
 addons: