switch to using go modules (#315)

* switch to using vgo

* update vendor dependencies

remove vendor dependencies

* add go modules to drone

* change environment variable syntax

* add environment variable to benchmark

* add git as build dependency

* change dockerfile logic

.drone.yml

@@ -6,13 +6,17 @@ pipeline:
   test:
     secrets: [ codecov_token ]
     image: golang:1.12
+    environment:
+      GO111MODULE: "on"
     commands:
       - make test
       - make coverage.txt
       - ./ci/codecov.sh
 
   benchmarks:
     image: golang:1.12
+    environment:
+      GO111MODULE: "on"
     commands:
       - make bench
 

Dockerfile

@@ -1,10 +1,22 @@
-FROM golang:1.12-alpine3.10 as build
-RUN apk add --no-cache make
-WORKDIR /go/src/github.com/uswitch/kiam
-ADD . .
+FROM golang:1.12.5 as build
+ENV GO111MODULE=on
+
+WORKDIR /workspace
+# Copy the Go Modules manifests
+COPY go.mod go.mod
+COPY go.sum go.sum
+# cache deps before building and copying source so that we don't need to re-download as much
+# and so that source changes don't invalidate our downloaded layer
+RUN go mod download
+
+COPY cmd/ cmd/
+COPY pkg/ pkg/
+COPY proto/ proto/
+COPY Makefile Makefile
+
 RUN make bin/kiam-linux-amd64
 
 FROM alpine:3.8
 RUN apk --no-cache add iptables
-COPY --from=build /go/src/github.com/uswitch/kiam/bin/kiam-linux-amd64 /kiam
+COPY --from=build /workspace/bin/kiam-linux-amd64 /kiam
 CMD []