root@server:~/docker# docker image build -t example/echo:latest .
Sending build context to Docker daemon  3.072kB
Step 1/4 : FROM golang:1.9
 ---> ef89ef5c42a9
Step 2/4 : RUN mkdir /echo
 ---> Using cache
 ---> 58f3cb19c839
Step 3/4 : COPY main.go /echo
 ---> b812938cbabc
Removing intermediate container c91757d70919
Step 4/4 : CMD go run /echo/main.go
 ---> Running in 5e76624a9714
 ---> 133a6f8f5426
Removing intermediate container 5e76624a9714
Successfully built 133a6f8f5426
Successfully tagged example/echo:latest
root@server:~/docker# docker image ls
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
example/echo        latest              133a6f8f5426        46 seconds ago      750MB
<none>              <none>              e5bf61deed81        8 minutes ago       750MB
golang              1.9                 ef89ef5c42a9        10 months ago       750MB