Try using go mod download instead of vendor (#47)

Author: Calebjh

Dockerfile

@@ -6,11 +6,10 @@ RUN apk add --no-cache git gcc musl-dev make
 WORKDIR /go/src/github.com/infobloxopen/migrate
 
 ENV GO111MODULE=on
-ENV GOFLAGS=""
 
 COPY go.mod go.sum ./
 
-RUN go mod vendor
+RUN go mod download
 
 COPY . ./