Fixed so it actually works

Dockerfile

@@ -1,7 +1,8 @@
 FROM golang:1.11-stretch as builder
 WORKDIR /build
-COPY * ./
+COPY go.mod go.sum ./
 RUN go get
+COPY * ./
 RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o default-request-adder .
 
 FROM scratch