Launch a Golang web server using Docker

If you want to create a web server using Go the simplest way to deploy is using Docker.  Golang code is compiled to a binary and does not need a special environment to run.

Here is the simplest web server code in Go to get started. Save this as webserver.go

package main 
import (        
      "fmt" 
       "log"
        "net/http"
        "runtime"
      )

 func main() {
     http.HandleFunc("/", indexHandlerHelloWorld)    
     log.Fatal(http.ListenAndServe(":8080", nil))
 } 

func indexHandlerHelloWorld(w http.ResponseWriter, r *http.Request) {
      fmt.Fprintf(w, "Hello world, I'm running search on %s with an %s CPU ", runtime.GOOS, runtime.GOARCH) 
}

We can use the simplest docker image scratch and add a directive to copy the binary to the server. Save as Dockerfile.

FROM scratch 
MAINTAINER Maria De Souza <maria.g.desouza@gmail.com> 

ADD go-webserver go-webserver 
ENTRYPOINT ["/go-webserver"] 
EXPOSE 8080

We setup a start shell script to build and kick up the docker

#!/bin/bash 
GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -a -o go-webserver webserver.go || exit 1 

if [ "$(docker ps -q -f name=go-web-server)" ]; then 
 docker stop $(docker ps -a -q --filter name=go-web-server --format="{{.ID}}") 
fi 

docker build -t go-web-server . || exit 1 

docker run -p 8000:8080 go-web-server || exit 1

You can use the -h option to add the hostname to the webserver

Voila! Now your webserver is running. Navigate to http://localhost:8000/ to test.

Known Issue

If you make any SSL requests from your webserver, you will see the following error when running the webserver using Docker:

x509: failed to load system roots and no roots provided

This is because the /etc/ssl/certs/ca-certificates.crt, is missing from the scratch image that is read by the golang tls package.

To avoid this copy the cert to your docker image from your local system. I normally add this to my bash script that will copy it based on OS.

if [ ! -e ca-certificates.crt ]; then  
if [[ $(uname) = "Darwin" ]]; then  
 cp /usr/local/etc/openssl/cert.pem ca-certificates.crt || exit 1  
else   
 cp /etc/ssl/certs/ca-certificates.crt ca-certificates.crt ||   exit 1  
 fi 
fi

This is what your Dockerfile should then look like:

FROM scratch  
MAINTAINER Maria De Souza <maria.g.desouza@gmail.com>  

COPY ca-certificates.crt /etc/ssl/certs/ca-certificates.crt 

ADD go-webserver go-webserver  
ENTRYPOINT ["/go-webserver"]  
EXPOSE 8080