go-modules with Docker
Project Folder
Create a project outside of $GOPATH, e.g. ~/Documents/<your-project-name>.
$ mkdir ~/Documents/go-modules && cd ~/Documents/go-modulesInit go modules
Init go modules by specifying the project namespace:
$ go mod init <project-namespace>
# E.g.
$ go mod init go-modulesAny packages that you create within this project will have the namespace go-modules.
main
Create a bare main.go file and include this:
package main
import (
"fmt"
"log"
"net/http"
"github.com/julienschmidt/httprouter"
)
func main() {
r := httprouter.New()
r.GET("/", func(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
fmt.Fprint(w, "hello world")
})
log.Println("listening to port *:8080. press ctrl + c to cancel.")
log.Fatal(http.ListenAndServe(":8080", r))
}pkg
Create a folder called pkg and include a greet package:
// pkg/greet/greet.go
package greet
const Version = 1Change your main.go file to call the greet package. It should look like this:
package main
import (
"fmt"
"log"
"net/http"
"go-modules/pkg/greet" // go-modules is our project namespace
"github.com/julienschmidt/httprouter"
)
func main() {
r := httprouter.New()
r.GET("/", func(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
fmt.Fprintf(w, "hello world, v%v", greet.Version)
})
log.Println("listening to port *:8080. press ctrl + c to cancel.")
log.Fatal(http.ListenAndServe(":8080", r))
}Vendor
This command will create a vendor directory locally for external dependencies. This is useful when building the binary (especially in Docker), as you do not need to fetch the dependencies again:
$ go mod vendorDockerize
A simplified multi-stage docker build Dockerfile would look like this:
FROM golang:1.11.0-stretch as builder
WORKDIR /go-modules
COPY . ./
# Building using -mod=vendor, which will utilize the v
RUN CGO_ENABLED=0 GOOS=linux go build -mod=vendor -o app
FROM alpine:3.8
WORKDIR /root/
COPY --from=builder /go-modules/app .
CMD ["./app"]Refer here for a more complete example.
Run the docker build:
# Build
$ docker build --no-cache -t alextanhongpin/go-modules .
# Run the image
$ docker run -d -p 8080:8080 alextanhongpin/go-modules
# Test
$ curl http://localhost:8080
hello world, v1%