Add GOPATH/bin to PATH

As stated in this issue, you can't run tools installed using go get without first updating $PATH.
actions/setup-go#14

Also add -set_exit_status to make golint return 1 if any issues are found.
https://github.com/golang/lint/blob/master/golint/golint.go#L24

.github/workflows/go.yml

@@ -22,8 +22,9 @@ jobs:
     - name: Run static analysis
       run: |
         go vet ./...
+        export PATH=$PATH:$(go env GOPATH)/bin
         go get -u golang.org/x/lint/golint    
-        golint ./...
+        golint -set_exit_status ./...
       
 
   test: