1.多阶段制作镜像，能够将镜像制作的很小

• 原始镜像

[root@moban go-docerfile]# cat Dockerfile 
FROM golang:1.14.4-alpine as builder
WORKDIR /opt
COPY main.go /opt
RUN go build /opt/main.go
CMD "./main"
[root@moban go-docerfile]# 
[root@moban go-docerfile]# 
[root@moban go-docerfile]# cat main.go 
package main

import "fmt"

func main() {  
    fmt.Println("Hello World")
}
[root@moban go-docerfile]# 

#制作镜像
[root@moban go-docerfile]# docker build -t go:hello_world . 

# 查看镜像的大小
[root@moban go-docerfile]# docker images|grep go
go             hello_world     673f39523712   41 minutes ago   372MB

• 多阶段制作镜像

[root@moban go-docerfile]# cat Dockerfile 
# build step
FROM golang:1.14.4-alpine
WORKDIR /opt
COPY main.go /opt
RUN go build /opt/main.go
CMD "./main"

# create real app image
FROM alpine:3.8
COPY --from=0 /opt/main /
CMD "./main"
[root@moban go-docerfile]# docker build -t go:alpine .

#查看镜像的大小
[root@moban go-docerfile]# docker images
REPOSITORY     TAG             IMAGE ID       CREATED          SIZE
go             alpine          55644e7ca51b   34 seconds ago   6.48MB

(原来的镜像大小372M，现在的镜像6.48M)
[root@moban go-docerfile]# docker run --rm go:alpine 
Hello World
[root@moban go-docerfile]# 

如果 FROM 多的话 可以用别名 
[root@moban go-docerfile]# cat Dockerfile 
# build step
FROM golang:1.14.4-alpine as builder
WORKDIR /opt
COPY main.go /opt
RUN go build /opt/main.go
CMD "./main"

# create real app image
FROM alpine:3.8
COPY --from=builder /opt/main /
CMD "./main"