add circleci

Author: aperezg

.circleci/config.yml

@@ -0,0 +1,68 @@
+version: 2.1
+jobs:
+  build-go1_11_6:
+    docker:
+      - image: circleci/golang:1.11.6
+        environment:
+          GO111MODULE: "on"
+    working_directory: /go/src/github.com/friendsofgo/errors
+    steps:
+      - checkout
+      - run: go test -v -race ./...
+      - run: go build -race cmd/killgrave/main.go
+  build-go1_12_9:
+    docker:
+      - image: circleci/golang:1.12.9
+        environment:
+          GO111MODULE: "on"
+    working_directory: /go/src/github.com/friendsofgo/errors
+    steps:
+      - checkout
+      - run: go test -v -race ./...
+  build-go1_13:
+    docker:
+      - image: circleci/golang:1.13
+    working_directory: /go/src/github.com/friendsofgo/errors
+    steps:
+      - checkout
+      - run: go test -v -race ./...
+  build-go_latest:
+    docker:
+      - image: circleci/golang:latest
+        environment:
+          GO111MODULE: "on"
+    working_directory: /go/src/github.com/friendsofgo/errors
+    steps:
+      - checkout
+      - run: go test -v -race ./...
+  coverage:
+    docker:
+      - image: circleci/golang:latest
+        environment:
+          GO111MODULE: "on"
+    working_directory: /go/src/github.com/friendsofgo/errors
+    steps:
+      - checkout
+      - run: make coverage
+      - run: bash <(curl -s https://codecov.io/bash)
+  release:
+    docker:
+      - image: circleci/golang:latest
+    steps:
+      - checkout
+      - run: curl -sL https://git.io/goreleaser | bash
+workflows:
+  version: 2
+  build_and_test:
+    jobs:
+      - build-go1_11_6
+      - build-go1_12_9
+      - build-go1_13
+      - build-go_latest
+      - coverage
+      - release:
+          filters:
+            branches:
+              ignore: /.*/
+            tags:
+              only: /v[0-9]+(\.[0-9]+)*(-.*)*/

Makefile

@@ -1,5 +1,7 @@
 [![FriendsOfGo](https://img.shields.io/badge/powered%20by-Friends%20of%20Go-73D7E2.svg)](https://friendsofgo.tech)
+[![CircleCI](https://circleci.com/gh/friendsofgo/errors.svg?style=svg)](https://circleci.com/gh/friendsofgo/errors)
 [![Build status](https://ci.appveyor.com/api/projects/status/phjkr6de4mnb19kq?svg=true)](https://ci.appveyor.com/project/aperezg/errors)
+[![Version](https://img.shields.io/github/release/friendsofgo/errors.svg?style=flat-square)](https://github.com/friendsofgo/errors/releases/latest)
 [![Go Report Card](https://goreportcard.com/badge/github.com/friendsofgo/errors)](https://goreportcard.com/report/github.com/friendsofgo/errors)
 [![GoDoc](https://godoc.org/github.com/friendsofgo/errors?status.svg)](https://godoc.org/github.com/friendsofgo/errors)