old Go versions doesn't support macos-latest

Author: shogo82148

.github/workflows/go.yml

@@ -32,6 +32,19 @@ jobs:
           - "1.12"
           - "1.11"
 
+        # old Go versions doesn't support macos-latest
+        exclude:
+          - os: macos-latest
+            go: "1.15"
+          - os: macos-latest
+            go: "1.14"
+          - os: macos-latest
+            go: "1.13"
+          - os: macos-latest
+            go: "1.12"
+          - os: macos-latest
+            go: "1.11"
+
     steps:
       - name: Check out code into the Go module directory
         uses: actions/checkout@v4