chore: migrate to go module (v3.0.0)

- chore: update dependencies: use version with go modules.
- chore: remove dep.
- chore: update backoff imports.
- chore: init go module.
- chore: update CI.
- chore: mod v3
- chore: update docker image.

.travis.yml

@@ -19,17 +19,13 @@ addons:
   - xn--lg-bja9b.wtf
 
 env:
-  - MEMCACHED_HOSTS=localhost:11211
+  - MEMCACHED_HOSTS=localhost:11211 GO111MODULE=on
 
 before_install:
   - '[ "${TRAVIS_PULL_REQUEST}" = "false" ] && openssl aes-256-cbc -K $encrypted_26c593b079d9_key -iv $encrypted_26c593b079d9_iv -in .gitcookies.enc -out .gitcookies -d || true'
 
-  # Download and install dep
-  - curl -sI https://github.com/golang/dep/releases/latest | grep -Fi Location  | tr -d '\r' | sed "s/tag/download/g" | awk -F " " '{ print $2 "/dep-linux-amd64"}' | wget --output-document=$GOPATH/bin/dep -i -
-  - chmod +x $GOPATH/bin/dep
-
   # Install Pebble and challtestsrv
-  - go get -u github.com/letsencrypt/pebble/...
+  - GO111MODULE=off go get -u github.com/letsencrypt/pebble/...
 
   # Install linters and misspell
   - curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | bash -s -- -b $GOPATH/bin v1.17.1
@@ -41,7 +37,7 @@ before_install:
 
 install:
   - echo "TRAVIS_GO_VERSION=$TRAVIS_GO_VERSION"
-  - dep status -v
+  - go mod download
 
 before_script:
   - make validate-doc

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## [v3.0.0] - 2019-08-05
+
+### Changed:
+- migrate to go module (new import github.com/go-acme/lego/v3/)
+- update DNS clients
+
 ## [v2.7.2] - 2019-07-30
 
 ### Fixed:

Dockerfile

@@ -1,13 +1,12 @@
-FROM golang:alpine3.9 as builder
+FROM golang:1.12-alpine3.10 as builder
 
-RUN apk --update upgrade \
-    && apk --no-cache --no-progress add make git
+RUN apk --no-cache --no-progress add make git
 
 WORKDIR /go/src/github.com/go-acme/lego
 COPY . .
 RUN make build
 
-FROM alpine:3.9
+FROM alpine:3.10
 RUN apk update \
     && apk add --no-cache ca-certificates tzdata \
     && update-ca-certificates