support etcd client v3 && support go mod

Dockerfile

@@ -1,17 +1,14 @@
-FROM golang:1.9.4-alpine3.7 AS builder
+FROM golang:1.16.2 AS builder
 WORKDIR /go/src/github.com/gliderlabs/registrator/
 COPY . .
 RUN \
-	apk add --no-cache curl git \
-	&& curl https://raw.githubusercontent.com/golang/dep/master/install.sh | sh \
-	&& dep ensure -vendor-only \
-	&& CGO_ENABLED=0 GOOS=linux go build \
+	CGO_ENABLED=0 GOOS=linux go build \
 		-a -installsuffix cgo \
 		-ldflags "-X main.Version=$(cat VERSION)" \
 		-o bin/registrator \
 		.
 
-FROM alpine:3.7
+FROM alpine:3.13
 RUN apk add --no-cache ca-certificates
 COPY --from=builder /go/src/github.com/gliderlabs/registrator/bin/registrator /bin/registrator
 

Dockerfile.dev

@@ -1,13 +1,6 @@
-FROM alpine:3.7
+FROM golang:1.16.2
 CMD ["/bin/registrator"]
 
 COPY . /go/src/github.com/gliderlabs/registrator
-RUN apk --no-cache add -t build-deps build-base go git curl \
-	&& apk --no-cache add ca-certificates \
-	&& export GOPATH=/go && mkdir -p /go/bin && export PATH=$PATH:/go/bin \
-	&& curl https://raw.githubusercontent.com/golang/dep/master/install.sh | sh \
-	&& cd /go/src/github.com/gliderlabs/registrator \
-	&& export GOPATH=/go \
-	&& git config --global http.https://gopkg.in.followRedirects true \
-	&& dep ensure \
+RUN cd /go/src/github.com/gliderlabs/registrator \
 	&& go build -ldflags "-X main.Version=dev" -o /bin/registrator