仅在其他软件包中使用变量时，如何避免“已声明且未使用”？

I saw this post How to avoid annoying error "declared and not used"

but I don't know if this is the right way to handle the error, when I use the variable in other packages.

for example, in case I use Connect() only in other packages, I don't use variable db in this package.

func Connect() {
  db, err := sql.Open("mysql", "root:Berlin2018@/jplatform")
  if err != nil {
    panic(err.Error())
  }
}

the best way to avoid the "annoying" declared and not used you shouldn't declare a variable that you are not using, if for instance you are not need to use an variable that returns from a function you can use _ to ignore it. like in here:

func Connect() {
  _, err := sql.Open("mysql", "root:Berlin2018@/jplatform")
  if err != nil {
    panic(err.Error())
  }
}

But you will need use your DB instance at other parts of your code so you will need to declare your variable with like that:

var DBInstance *sql.db

and then you will be able to access the db pointer from anywhere in the package

so full example will be:

var DBInstance *sql.db
func Connect() {
      db, err := sql.Open("mysql", "root:Berlin2018@/jplatform")
      if err != nil {
        panic(err.Error())
      }
    }