feat(ci): add Makefile and GitHub Actions configuration

And also enable printing conver's own version with `-version` option.

Makefile

@@ -0,0 +1,154 @@
+NAME := conver
+ROOT := $(CURDIR)
+SOURCES := $(shell find . -name "*.go" -or -name "go.mod" -or -name "go.sum" \
+	-or -name "Makefile")
+
+# Verbose output
+ifdef VERBOSE
+V = -v
+endif
+
+#
+# Environment
+#
+
+BINDIR := bin
+TOOLDIR := tools/bin
+
+# Global environment variables for all targets
+SHELL ?= /bin/bash
+SHELL := env \
+	GO111MODULE=on \
+	GOBIN=$(CURDIR)/$(TOOLDIR) \
+	CGO_ENABLED=1 \
+	PATH='$(CURDIR)/$(BINDIR):$(CURDIR)/$(TOOLDIR):$(PATH)' \
+	$(SHELL)
+
+#
+# Defaults
+#
+
+# Default target
+.DEFAULT_GOAL := build
+
+.PHONY: all
+all: lint test build
+
+#
+# Tools
+#
+
+TOOLS += $(TOOLDIR)/gobin
+gobin: $(TOOLDIR)/gobin
+$(TOOLDIR)/gobin:
+	GO111MODULE=off go get -u github.com/myitcv/gobin
+
+# external tool
+define tool # 1: binary-name, 2: go-import-path
+TOOLS += $(TOOLDIR)/$(1)
+
+.PHONY: $(1)
+$(1): $(TOOLDIR)/$(1)
+
+$(TOOLDIR)/$(1): $(TOOLDIR)/gobin Makefile
+	gobin $(V) "$(2)"
+endef
+
+$(eval $(call tool,gofumports,mvdan.cc/gofumpt/gofumports))
+$(eval $(call tool,golangci-lint,github.com/golangci/golangci-lint/cmd/golangci-lint@v1.31))
+
+.PHONY: tools
+tools: $(TOOLS)
+
+#
+# Build
+#
+
+BINARY=$(BINDIR)/$(NAME)
+LDFLAGS := -w -s
+
+VERSION ?= $(shell git describe --tags 2>/dev/null)
+GIT_SHA ?= $(shell git rev-parse --short HEAD 2>/dev/null)
+DATE ?= $(shell date +%s)
+
+ifeq ($(trim $(VERSION)),)
+	VERSION = dev
+endif
+
+.PHONY: build
+build: $(BINARY)
+
+$(BINARY): $(SOURCES)
+	go build $(V) -a -o "$@" -ldflags "$(LDFLAGS) \
+		-X main.Version=$(VERSION) \
+		-X main.Commit=$(GIT_SHA) \
+		-X main.Date=$(DATE)"
+
+#
+# Development
+#
+
+.PHONY: clean
+clean:
+	rm -rf $(BINS) $(TOOLS)
+	rm -f ./coverage.out ./go.mod.tidy-check ./go.sum.tidy-check
+
+.PHONY: test
+test:
+	go test $(V) -count=1 --race ./...
+
+.PHONY: lint
+lint: $(TOOLS)
+	$(info Running Go linters)
+	GOGC=off golangci-lint $(V) run
+
+.PHONY: format
+format: gofumports
+	gofumports -w .
+
+#
+# Coverage
+#
+
+.PHONY: cov
+cov: coverage.out
+
+.PHONY: cov-html
+cov-html: coverage.out
+	go tool cover -html=coverage.out
+
+.PHONY: cov-func
+cov-func: coverage.out
+	go tool cover -func=coverage.out
+
+coverage.out: $(SOURCES)
+	go test $(V) -covermode=count -coverprofile=coverage.out ./...
+
+#
+# Dependencies
+#
+
+.PHONY: deps
+deps:
+	$(info Downloading dependencies)
+	go mod download
+
+.PHONY: tidy
+tidy:
+	go mod tidy $(V)
+
+.PHONY: verify
+verify:
+	go mod verify
+
+.SILENT: check-tidy
+.PHONY: check-tidy
+check-tidy:
+	cp go.mod go.mod.tidy-check
+	cp go.sum go.sum.tidy-check
+	go mod tidy
+	-diff go.mod go.mod.tidy-check
+	-diff go.sum go.sum.tidy-check
+	-rm -f go.mod go.sum
+	-mv go.mod.tidy-check go.mod
+	-mv go.sum.tidy-check go.sum