Can't access Go REST API using docker-compose

php editor Yuzai found that many developers encountered a common problem when using docker-compose, that is, they were unable to access the Go REST API. This problem may prevent developers from properly testing and debugging APIs. In this article, we will share some methods and techniques to solve this problem to help developers successfully use docker-compose to access the Go REST API and improve development efficiency.

Question content

I'm trying to run a simple go rest api using gin gonic and mysql and phpmyadmin and docker.

Although phpmyadmin is running fine, when I try to access my go api, I get the following error message: localhost did not send any data. err_empty_response

If I run the main.go file without docker, everything works as expected

This is my docker-compose file

version: '3'
services:
  app:
    container_name: full_app
    build: .
    ports:
      - 8080:8080
    expose:
      - 8080
    restart: on-failure
    environment:
      - pma_host=fullstack-mysql
      - db_name=${db_name}
      - db_user=${db_user}
      - db_password=${db_port}
    volumes:
      - .:/usr/src/app/
    depends_on:
      - fullstack-mysql
    networks:
      - fullstack

  fullstack-mysql:
    image: mysql:5.7
    container_name: full_db_mysql
    ports:
      - 3306:3306
    environment:
      - mysql_root_host=${db_host}
      - mysql_user=${db_user}
      - mysql_root_user=${db_root_user}
      - mysql_password=${db_password}
      - mysql_root_password=${db_root_password}
      - mysql_database=${db_name}
      - mysql_root_password=${db_password}
    volumes:
      - database_mysql:/var/lib/mysql
    networks:
      - fullstack

  phpmyadmin:
    image: phpmyadmin/phpmyadmin
    container_name: phpmyadmin_container
    depends_on:
      - fullstack-mysql
    environment:
      - pma_host=fullstack-mysql
      - pma_user=${db_user}
      - pma_port=${db_port}
      - pma_password=${db_password}
    ports:
      - 9090:80
    restart: always
    networks:
      - fullstack

volumes:
  api:
  database_mysql:

# networks to be created to facilitate communication between containers
networks:
  fullstack:
    driver: bridge

This is my dockerfile:

# start from golang base image
from golang:alpine as builder

# env go111module=on

# install git.
# git is required for fetching the dependencies.
run apk update && apk add --no-cache git

# set the current working directory inside the container
workdir /app

# copy go mod and sum files
copy go.mod go.sum ./

# download all dependencies. dependencies will be cached if the go.mod and the go.sum files are not changed
run go mod download

# copy the source from the current directory to the working directory inside the container
copy . .

# build the go app
run cgo_enabled=0 goos=linux go build -a -installsuffix cgo -o main .

# start a new stage from scratch
from alpine:latest
run apk --no-cache add ca-certificates

workdir /root/

# copy the pre-built binary file from the previous stage. observe we also copied the .env file
copy --from=builder /app/main .
copy --from=builder /app/.env .

# expose port 8080 to the outside world
expose 8080

#command to run the executable
cmd ["./main"]

This is my go main.go file (currently):

package main

import (
    "github.com/gin-gonic/gin"
    "log"
    "net/http"
)

func main() {
    router := gin.Default()

    router.GET("/", func(context *gin.Context) {
        context.JSON(http.StatusOK, gin.H{"data": "Hello World !"})
    })

    router.Run("localhost:8080")
}

If I visit http://localhost:9090 phpmyadmin is loading (exactly what I expect) If I visit http://localhost:8080 I get this error message: localhost sent no data. err_empty_response

I run docker-compose up --build for this. I'm obviously doing something wrong, but I'm not sure what.

Workaround

The problem seems to be with your go code and the way I specify the listening host for the api. In my main.go file I currently have the host set to "localhost:8080", but when running my application inside a docker container I should be listening on "0.0.0.0:8080" . This allows the container to bind to all network interfaces.

To resolve this issue, I had to modify the router.run line in the main.go file as follows:

router.Run("0.0.0.0:8080")

After making this change, I rebuilt the docker image and used docker-compose up --build to run the container again. This should allow access to my go rest api on http://localhost:8080 outside the docker container.

Note: localhost in the container refers to the container itself, not the host. By using "0.0.0.0" I'm instructing the container to bind to all available network interfaces, allowing me to access the api from the host.

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