update dir structure for main.go in Dockerfile

Author: estroz

pkg/scaffold/build_dockerfile.go

@@ -45,7 +45,7 @@ ENV GOARCH amd64
 WORKDIR /go/src/{{ .Repo }}
 COPY . /go/src/{{ .Repo }}
 
-RUN go build -o /go/bin/{{ .ProjectName }} {{ .Repo }}/cmd/{{ .ProjectName }}/main.go
+RUN go build -o /go/bin/{{ .ProjectName }} {{ .Repo }}/cmd/manager/main.go
 
 # Base image
 FROM alpine:3.6