Replace deprecated dep dependency with go mod

Dockerfile

@@ -1,12 +1,19 @@
 # build stage
 FROM golang:latest AS build-env
-RUN go get github.com/golang/dep/cmd/dep
-RUN go get -d github.com/GoogleCloudPlatform/k8s-node-termination-handler || true
-WORKDIR /go/src/github.com/GoogleCloudPlatform/k8s-node-termination-handler
+
+WORKDIR /build
+
+COPY go.mod .
+COPY go.sum .
+
+RUN go mod download
+
+COPY . .
+
 RUN CGO_ENABLED=0 GOOS=linux go build -a -ldflags '-extldflags "-static"' -tags netgo -o node-termination-handler
 
 # final stage
 FROM gcr.io/distroless/static:latest
 WORKDIR /app
-COPY --from=build-env /go/src/github.com/GoogleCloudPlatform/k8s-node-termination-handler/node-termination-handler /app/
+COPY --from=build-env /build/node-termination-handler /app/
 ENTRYPOINT ["./node-termination-handler"]

Dockerfile.build

@@ -1,12 +1,19 @@
 # build stage
 FROM golang:latest AS build-env
-RUN go get github.com/golang/dep/cmd/dep
-WORKDIR /go/src/github.com/GoogleCloudPlatform/k8s-node-termination-handler
+
+WORKDIR /build
+
+COPY go.mod .
+COPY go.sum .
+
+RUN go mod download
+
 COPY . .
+
 RUN CGO_ENABLED=0 GOOS=linux go build -a -ldflags '-extldflags "-static"' -tags netgo -o node-termination-handler && go test ./...
 
 # final stage
 FROM gcr.io/distroless/static:latest
 WORKDIR /app
-COPY --from=build-env /go/src/github.com/GoogleCloudPlatform/k8s-node-termination-handler/node-termination-handler /app/
-ENTRYPOINT [./node-termination-handler]
+COPY --from=build-env /build/node-termination-handler /app/
+ENTRYPOINT ["./node-termination-handler"]