docker-compose.yaml

version: '3.6'

services:
  database:
    restart: always
    image: mysql:5.6
    ports:
      - "3306:3306"
    environment:
      - MYSQL_ROOT_PASSWORD=123456
      - MYSQL_USER=test
      - MYSQL_PASSWORD=test
      - MYSQL_DATABASE=test
  app:
    build: .
    restart: always
    depends_on:
      - database
    volumes:
     - .:/code

Dockerfile

FROM golang
COPY . /code
ENV GO111MODULE on
WORKDIR /code
RUN ["go", "run", "-mod=vendor", "main.go"]

main.go

package main

import (
	"fmt"
	"os"
	"time"

	"github.com/go-sql-driver/mysql"
	"github.com/jmoiron/sqlx"
)

func main() {
	conf := mysql.NewConfig()
	conf.User = "root"
	conf.Passwd = "123456"
	conf.Addr = "database:3306"
	conf.DBName = "test"
	conf.Net = "tcp"
	dsn := conf.FormatDSN()

	for i := 0; i <= 60; i++ {
		_, err := sqlx.Connect("mysql", dsn)
		if err == nil {
			os.Exit(0)
		}
		fmt.Println(err)
		time.Sleep(1 * time.Second)
	}

	os.Exit(1)
}