main.go

Let's create a bare minimum Go program so that we can use it in the Docker image. It will take the NAME environmental variable and print <NAME> is your uncle. and then quit:

package main 
 
import ( 
    "fmt" 
    "os" 
) 
 
func main() { 
    fmt.Println(os.Getenv("NAME") + " is your uncle.") 
} 

Now that we have all the code in place, let's build the Docker image using the Dockerfile file:

$ cd docker
$ tree
.
├── Dockerfile
└── main.go"
0 directories, 2 files 
 
$ # -t tag lets us name our docker images so that we can easily refer to them 
 
$ docker build . -t hello-uncle  
Sending build context to Docker daemon 3.072 kB 
Step 1/5 : FROM golang:1.9.1 
 ---> 99e596fc807e 
Step 2/5 : ADD . /go/src/hello 
 ---> Using cache 
 ---> 64d080d7eb39 
Step 3/5 : RUN go install hello 
 ---> Using cache 
 ---> 13bd4a1f2a60 
Step 4/5 : ENV NAME Bob 
 ---> Using cache 
 ---> cc432fe8ffb4 
Step 5/5 : ENTRYPOINT /go/bin/hello 
 ---> Using cache 
 ---> e0bbfb1fe52b 
Successfully built e0bbfb1fe52b 
 
$ # Let's now try to run the docker image. 
$ docker run hello-uncle 
Bob is your uncle. 
 
$ # We can also change the environment variables on the fly. 
$ docker run  -e NAME=Sam hello-uncle 
Sam is your uncle.