仅当ECS时才能在Golang中连接到RDS mysql

Question

I try to lunch application in ECS.
There is no problem when lunching in my local docker environment.
But it can't accrss to api server in ECS because of rds connection problem.

I use golang in api server and mysql for db.
I call db.go in main.go

func main() {

    db := db.NewDatabase(os.Getenv("MYSQL_USER"), os.Getenv("MYSQL_PASSWORD"), os.Getenv("MYSQL_HOST"))

Error occurs when connecting to rds database

func NewDatabase(user, password, host string) *Database {
    db, err := sql.Open("mysql", user+":"+password+"@tcp("+host+":3306)/article")
    if err != nil {
        panic(err.Error())
    }

    err = db.Ping()
    // error occurs here
    if err != nil {
        panic(err.Error())
    }

I deploy it to elastic beanstalk.
I checked environment variables are correctly set.

Here is the full source code:
https://github.com/jpskgc/article

I expect there is no error in elastic beans.
But the actual is not.
I want to know solution for that.

Here is the error log in elastic beanstalk.

-------------------------------------
/var/log/containers/server-4c66c8d1848a-stdouterr.log
-------------------------------------
panic: dial tcp 172.31.26.91:3306: connect: connection timed out

goroutine 1 [running]:
article/api/db.NewDatabase(0xc00002401b, 0x4, 0xc00002a00f, 0xb, 0xc00002800b, 0x3c, 0xdb94f2)
    /app/db/db.go:20 +0x3bc
main.main()
    /app/main.go:18 +0xee

Answer 1

"connection timed out" means that there are firewall limitation, and you can also check your mysql whitelist, which should has ip of your ECS.