SpringBootでのDBアクセスエラーの解決法

前提・実現したいこと

以下のサイトを参考にして勉強しています

前提としてDocker上で動かしており、ツールはIntelliJ IDEAを使用しています。

途中のFlywayの項まで進めたのですがコンパイルしようとするとエラーが発生しました。量が多く同じエラーの繰り返しなので一部を載せます。

発生している問題・エラーメッセージ

2020-12-24 14:01:38.640  INFO 115 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.41]
2020-12-24 14:01:39.124  INFO 115 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2020-12-24 14:01:39.125  INFO 115 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 14247 ms
2020-12-24 14:01:40.746  INFO 115 --- [           main] o.f.c.internal.license.VersionPrinter    : Flyway Community Edition 7.1.1 by Redgate
2020-12-24 14:01:40.893  INFO 115 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2020-12-24 14:01:46.900  INFO 115 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
2020-12-24 14:02:16.945  WARN 115 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'flywayInitializer' defined in class path resource [org/springframework/boot/autoconfigure/flyway/FlywayAutoConfiguration$FlywayConfiguration.class]: Invocation of init method failed; nested exception is org.flywaydb.core.internal.exception.FlywaySqlException: 
Unable to obtain connection from database: HikariPool-1 - Connection is not available, request timed out after 30002ms.
-----------------------------------------------------------------------------------------------------------------------
SQL State  : 08001
Error Code : 0
Message    : Could not create connection to database server. Attempted reconnect 3 times. Giving up.

2020-12-24 14:02:16.945  INFO 115 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2020-12-24 14:02:22.978  INFO 115 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.
2020-12-24 14:02:23.011  INFO 115 --- [           main] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2020-12-24 14:02:23.072  INFO 115 --- [           main] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2020-12-24 14:02:23.263 ERROR 115 --- [           main] o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'flywayInitializer' defined in class path resource [org/springframework/boot/autoconfigure/flyway/FlywayAutoConfiguration$FlywayConfiguration.class]: Invocation of init method failed; nested exception is org.flywaydb.core.internal.exception.FlywaySqlException: 
Unable to obtain connection from database: HikariPool-1 - Connection is not available, request timed out after 30002ms.
-----------------------------------------------------------------------------------------------------------------------
SQL State  : 08001
Error Code : 0
Message    : Could not create connection to database server. Attempted reconnect 3 times. Giving up.

-----------------------------------------------------------------------------------------------------------------------
SQL State  : 08001
Error Code : 0
Message    : Could not create connection to database server. Attempted reconnect 3 times. Giving up.

ソースコード

docker-comopse.yml

version: '3'
services:
  app:
    image: openjdk:14-jdk-alpine
    ports:
      - "80:8080"
    volumes:
      - .:/app
    working_dir: /app
    command: ./gradlew bootRun
    environment:
      DATASOURCE: jdbc:mysql://db:3306/springboot-flyway
  db:
    image: mysql:5.7
    environment:
      MYSQL_ROOT_PASSWORD: password
      MYSQL_DATABASE: springboot-flyway
      MYSQL_USER: user
      MYSQL_PASSWORD: passwrod
    command: mysqld --character-set-server=utf8 --collation-server=utf8_unicode_ci --default-time-zone=Asia/Tokyo
    volumes:
      - ./docker/mysql:/docker-entrypoint-initdb.d
    ports:
      - "3306:3306"

application.yml

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/springboot-flyway?autoReconnect=true&useSSL=false
    username: user
    password: password
    driver-class-name: com.mysql.cj.jdbc.Driver
    hikari:
      initialization-fail-timeout: 0

FlywayConfig.java

package shunp.geminiapi.config;

import org.springframework.boot.autoconfigure.flyway.FlywayMigrationStrategy;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class FlywayConfig {

    @Bean
    public FlywayMigrationStrategy strategy1111() {
        return flyway -> {
            // flyway_schema_historyの初期化
            flyway.clean();
            // マイグレーション実行
            flyway.migrate();
        };
    }
}

試したこと

最初はドライバーは存在しないといわれていたので'com.mysql.jdbc.Driber'から'con.mysql.cj.jdbc.Driver'に変更しました。
ほかにHikariCPというライブラリのエラーかと思ったのでオプションの指定を行ったりました。
MysqlのTimeZoneの設定を行いました。

###まとめ
数時間格闘したのですが解決方法がわかりません。どうか回答のほうお願いします。