为什么hikari连接池在同时接收多个请求时只使用1到2个连接？

import com.zaxxer.hikari.HikariDataSource;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Bean
    public HikariDataSource dataSource() {
        HikariDataSource dataSource = new HikariDataSource();
        dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/mydb");
        dataSource.setUsername("user");
        dataSource.setPassword("password");
        dataSource.setMaximumPoolSize(20);
        dataSource.setMinimumIdle(10);
        dataSource.setConnectionTimeout(30000);
        return dataSource;
    }
}