docker-compose upでMySQLが起動するまで待つ方法(2種類紹介)

docker-compose up -d
Creating network "api_network" with the default driver
Creating redis ... done
Creating mysql ... done
Creating api ... done

docker-compose ps
Name      Command         State         Ports              
--------------------------------------------------------------------------------------------------
mysql     .sh mysql ...   Up       0.0.0.0:3306->3306/tcp, 33060/tcp
redis     .sh redis ...   Up       0.0.0.0:6380->6380/tcp          
api       app/build/api   Exit 2

docker-compose logs api
api    | panic: dial tcp 172.28.0.3:3306: connect: connection refused 

# !/bin/.sh
# MySQLサーバーが起動するまでループで待機する

until mysqladmin ping -h mysql --silent; do
  echo 'waiting for mysqld to be connectable...'
  sleep 2
done

echo " go app is started!"
exec app/build/api

volumes:
      - ./api/scripts:/mnt
    entrypoint: mnt/start.sh

RUN apk update \
&& apk add mysql-client

docker-compose ps
Name      Command         State         Ports              
--------------------------------------------------------------------------------------------------
mysql     .sh mysql ...   Up       0.0.0.0:3306->3306/tcp, 33060/tcp
redis     .sh redis ...   Up       0.0.0.0:6380->6380/tcp          
api       ./api/scripts:start.sh   Up       0.0.0.0:8080->8080/tcp

db := mysql.ConnectDB()
    db.LogMode(true)
    defer db.Close()

import (
"github.com/jinzhu/gorm"
    _ "github.com/jinzhu/gorm/dialects/mysql"
"log"
"time"
)

var DB *gorm.DB
var err error
var count = 0

func connect(path string) (*gorm.DB, error) {
    db, err := gorm.Open("mysql", path)
    if err != nil {
        log.Println("Not ready. Retry connecting...")
        time.Sleep(time.Second)
        count++
        log.Println(count)
        if count > 30 {
            panic(err)
        }
        return connect(path)
    }
    log.Println("Successfully")
    return db, nil
}

docker-compose ps
Name      Command         State         Ports              
--------------------------------------------------------------------------------------------------
mysql     .sh mysql ...   Up       0.0.0.0:3306->3306/tcp, 33060/tcp
redis     .sh redis ...   Up       0.0.0.0:6380->6380/tcp          
api       app/build/api   Up       0.0.0.0:8080->8080/tcp

import (
    "fmt"
    "os"
    "strings"
    "time"

    "github.com/jinzhu/gorm"
    _ "github.com/jinzhu/gorm/dialects/mysql"
)

var DB *gorm.DB
var err error
// カウントの変数は削除

// openの第2引数をカウント、uintにする
func open(path string, count uint) (*gorm.DB, error) {
    db, err := gorm.Open("mysql", path)
    if err != nil {
        if count == 0 {
            return nil, fmt.Errorf("Retry count over")
        }
        time.Sleep(time.Second)
// カウントダウンさせるようにする
        count--
        return open(path, count)
    }
    return db, nil
}

// MySQLへの接続
func ConnectDB() *gorm.DB {
// openの引数に30のカウントを指定
db, err := open(path, 30)
    if err != nil {
        panic(err)
    }