Add explicit permissions to workflow

Author: mbg

.github/workflows/ci.yml

@@ -2,6 +2,9 @@ name: CI
 
 on: [push, pull_request]
 
+permissions:
+  contents: read
+
 jobs:
     build:
         name: Build
@@ -29,4 +32,4 @@ jobs:
               run: go get -v -t -d .
 
             - name: Build go
-              run: go build
+              run: go build