Ability to dockerize a Beego application

This introduces a new command "dockerize" which will generate
a Dockerfile to allow a Beego Web Application to run inside Docker.

bee.go

@@ -126,6 +126,7 @@ var availableCommands = []*Command{
 	//cmdRundocs,
 	cmdMigrate,
 	cmdFix,
+	cmdDockerize,
 }
 
 var logger = GetBeeLogger(os.Stdout)

dockerize.go

@@ -0,0 +1,112 @@
+// Copyright 2016 bee authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"): you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations
+// under the License.
+
+package main
+
+import (
+	"flag"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+	"text/template"
+)
+
+var cmdDockerize = &Command{
+	CustomFlags: true,
+	UsageLine:   "dockerize",
+	Short:       "Generates a Dockerfile for your Beego application",
+	Long: `Dockerize generates a Dockerfile for your Beego Web Application.
+  The Dockerfile will compile, get the dependencies with {{"godep"|bold}}, and set the entrypoint.
+  `,
+	PreRun: func(cmd *Command, args []string) { ShowShortVersionBanner() },
+	Run:    dockerizeApp,
+}
+
+const dockerBuildTemplate = `FROM library/golang:latest
+
+# Get Beego Web Framework
+RUN go get github.com/astaxie/beego
+
+# Godep for vendoring
+RUN go get github.com/tools/godep
+
+# Recompile the standard library without CGO
+RUN CGO_ENABLED=0 go install -a std
+
+ENV APP_DIR $GOPATH{{.Appdir}}
+RUN mkdir -p $APP_DIR
+
+# Set the entrypoint
+ENTRYPOINT $APP_DIR/{{.Entrypoint}}
+ADD . $APP_DIR
+
+# Compile the binary and statically link
+RUN cd $APP_DIR
+RUN CGO_ENABLED=0 godep go build -ldflags '-d -w -s'
+
+EXPOSE {{.Expose}}
+`
+
+type Dockerfile struct {
+	Appdir     string
+	Entrypoint string
+	Expose     string
+}
+
+var (
+	expose string
+)
+
+func init() {
+	fs := flag.NewFlagSet("dockerize", flag.ContinueOnError)
+	fs.StringVar(&expose, "expose", "8080", "Port to expose in the Docker container.")
+	cmdDockerize.Flag = *fs
+}
+
+func dockerizeApp(cmd *Command, args []string) int {
+	cmd.Flag.Parse(args)
+
+	logger.Info("Generating Dockerfile...")
+
+	gopath := os.Getenv("GOPATH")
+	dir, err := filepath.Abs(".")
+	MustCheck(err)
+
+	appdir := strings.Replace(dir, gopath, "", 1)
+
+	_, entrypoint := path.Split(appdir)
+	dockerfile := Dockerfile{
+		Appdir:     appdir,
+		Entrypoint: entrypoint,
+		Expose:     expose,
+	}
+
+	generateDockerfile(dockerfile)
+	return 0
+}
+
+func generateDockerfile(df Dockerfile) {
+	t := template.Must(template.New("dockerBuildTemplate").Parse(dockerBuildTemplate)).Funcs(BeeFuncMap())
+
+	f, err := os.Create("Dockerfile")
+	if err != nil {
+		logger.Fatalf("Error writing Dockerfile: %v", err.Error())
+	}
+	defer CloseFile(f)
+
+	t.Execute(f, df)
+
+	logger.Success("Dockerfile generated.")
+}