使用方式：

    1. $ gf docker -h
    2. USAGE
    3.     gf docker [FILE] [OPTION]
    5. ARGUMENT
    6.     FILE      file path for "gf build", it's "main.go" in default.
    7.     OPTION    the same options as "docker build" except some options as follows defined
    9. OPTION
    10.     -p, --push  auto push the docker image to docker registry if "-t" option passed
    12. EXAMPLES
    13.     gf docker
    14.     gf docker -t hub.docker.com/john/image:tag
    15.     gf docker -p -t hub.docker.com/john/image:tag
    16.     gf docker main.go
    17.     gf docker main.go -t hub.docker.com/john/image:tag
    18.     gf docker main.go -t hub.docker.com/john/image:tag
    19.     gf docker main.go -p -t hub.docker.com/john/image:tag
    21. DESCRIPTION
    22.     The "docker" command builds the GF project to a docker images.
    23.     It runs "gf build" firstly to compile the project to binary file.
    24.     It then runs "docker build" command automatically to generate the docker image.
    25.     You should have docker installed, and there must be a Dockerfile in the root of the project.

    自动编译并生成docker镜像。非必需FILE参数为编译文件路径，默认为main.go。非必需参数OPTIONS为docker build命令相同参数及选项。
    使用示例：

    1. $ gf docker main.go -p -t loads/gf-demos:test          
    2. 2020-12-31 00:47:28.207 start building...
    3. 2020-12-31 00:47:28.207 go build -o ./bin/linux_amd64/main main.go
    4. 2020-12-31 00:47:35.894 done!
    5. Sending build context to Docker daemon  37.63MB
    6. Step 1/10 : FROM loads/alpine:3.8
    7.  ---> f9fb622e6db2
    8. Step 2/10 : LABEL maintainer="john@goframe.org"
    9.  ---> Using cache
    10.  ---> da238418d031
    11. Step 3/10 : ENV WORKDIR /var/www/gf-demos
    12.  ---> Using cache
    13.  ---> 3e7129c087c9
    14. Step 4/10 : ADD ./bin/linux_amd64/main   $WORKDIR/main
    15.  ---> 3661a9dea494
    16. Step 5/10 : RUN chmod +x $WORKDIR/main
    17.  ---> Running in 1d49d5d91080
    18. Removing intermediate container 1d49d5d91080
    19.  ---> a03ee04e3380
    20. Step 6/10 : ADD public   $WORKDIR/public
    21.  ---> 63dd06d0e1a3
    22. Step 7/10 : ADD config   $WORKDIR/config
    23.  ---> fa7a57eba577
    24. Step 8/10 : ADD template $WORKDIR/template
    25.  ---> 7075609b0447
    26. Step 9/10 : WORKDIR $WORKDIR
    27.  ---> Running in a34ef38e1031
    28. Removing intermediate container a34ef38e1031
    29.  ---> 580077998eaf
    30. Step 10/10 : CMD ./main
    31.  ---> Running in ed286b518ad9
    32. Removing intermediate container ed286b518ad9
    33.  ---> fbbc05842901
    34. Successfully built fbbc05842901
    35. Successfully tagged loads/gf-demos:test
    36. The push refers to repository [docker.io/loads/gf-demos]
    37. b4025b95a79f: Preparing 
    38. 9e0369a57507: Preparing 
    39. 46c68dcc8e12: Preparing 
    40. 59adbc083ee5: Preparing 
    41. 10e0b999ba57: Preparing 
    42. 8e850d7b086e: Waiting 
    43. d5e057db20a2: Waiting 
    44. 92e898fd7f84: Waiting 
    45. d9ff549177a9: Waiting 
    46. ...