编译和运行分离

package main

import (
        "fmt"
        "log"
        "net/http"
        "os"
)

func main() {
        // register hello function to handle all requests
        mux := http.NewServeMux()
        mux.HandleFunc("/", hello)

        // use PORT environment variable, or default to 8080
        port := os.Getenv("PORT")
        if port == "" {
                port = "8080"
        }

        // start the web server on port and accept requests
        log.Printf("Server listening on port %s", port)
        log.Fatal(http.ListenAndServe(":"+port, mux))
}

// hello responds to the request with a plain-text "Hello, world" message.
func hello(w http.ResponseWriter, r *http.Request) {
        log.Printf("Serving request: %s", r.URL.Path)
        host, _ := os.Hostname()
        fmt.Fprintf(w, "Hello, world!\n")
        fmt.Fprintf(w, "Version: 1.0.0\n")
        fmt.Fprintf(w, "Hostname: %s\n", host)
}

Dockerfile:其中的 COPY 命令通过指定 --from=0 参数，把前一阶段构建的产物拷贝到了当前的镜像中。

FROM golang:1.8-alpine
ADD . /go/src/hello-app
RUN go install hello-app

FROM alpine:latest
COPY --from=0 /go/bin/hello-app .
ENV PORT 8080
CMD ["./hello-app"]

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