Use correct comment character

Author: Danny McCormick

README.md

@@ -19,7 +19,7 @@ steps:
 - uses: actions/checkout@master
 - uses: actions/setup-go@v1
   with:
-    go-version: '1.9.3' // The Go version to download (if necessary) and use.
+    go-version: '1.9.3' # The Go version to download (if necessary) and use.
 - run: go run hello.go
 ```