simple planetscale - golang app won't select the database properly

Question

After connecting to a Planetscale database using DSN with the following structure:

user:password@tcp(host)/database?tls=true

I decided to test it by running a simple query. Here's my main.go file:

package main

import (
    "database/sql"
    "fmt"
    "os"

    _ "github.com/go-sql-driver/mysql"
)

func GetDatabase() (*sql.DB, error) {
    db, err := sql.Open("mysql", os.Getenv("DSN"))
    return db, err
}

func main() {
    db, err := GetDatabase()
    if err != nil {
        panic(err)
    }
    if err := db.Ping(); err != nil {
        panic(err)
    }
    // ---
    query, err := db.Query("SELECT name FROM status;")
    if err != nil {
        panic(err.Error())
    }
    var name string
    for query.Next() {
        err = query.Scan(&name)
        if err != nil {
            panic(err.Error())
        }
        fmt.Println(name)
    }
    // ---
    fmt.Println("Successfully connected to PlanetScale!")
}

If I remove the section between the two comment lines, it will print out the 'successfully connected' message; however, if I try to run it including the query part, the outcome changes to: panic: Error 1046: No database selected

Well, I decided to try with the query:

"USE database; SELECT name FROM status;"

However, the default driver won't take multiple statements and returns syntax error.

I know it seems like a simple question, but I already read the documentation from planetscale, from the go mysql driver, and I haven't been able to overcome this little issue. Any help will be greatly appreciated.

Answer 1

Looks like the problem is with the .env file. If I save the same information to a string variable within the same GetDatabase() function, and then pass it as argument instead of os.Getenv(), it connects normally. Can't tell exactly why that happens, but if someone can provide further information, I'll be thankful.

Edit:

when saving my credentials to an .env file, and using the built-in function os.Getenv("DSN"), the program will indeed connect to planetscale, but it won't select the given database in the DSN string. As mentioned in the question, selecting the database first and then running statements / queries doesn't work because of the constraints of the driver.

If I hard code the variables to a string variable, eg:

dsn := "root:mlc@tcp(127.0.0.1:3306)/app"

and then use that to open the connection, this time the program will use the desired database with any problem.