Add golangci-lint to main Dockerfile

Author: stuartleeks

Dockerfile

@@ -9,6 +9,9 @@ COPY go.sum go.sum
 # and so that source changes don't invalidate our downloaded layer
 RUN go mod download
 
+# Install golangci-linter
+RUN curl -sfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh| sh -s -- -b $(go env GOPATH)/bin v1.21.0
+
 # Copy the go source
 COPY main.go main.go
 COPY api/ api/