短声明运算符遮盖全局变量

There is oneFunction that returns 2 values of types int and error. I want to assign the first value to already existing variable and assign second value to a new variable.

If I use short declaration operator :=, there will be created 2 new variables x and err.

var x int
x, err := oneFunction()

To get rid of creating new x variable I must not use := operator and declare err before calling oneFunction

    var x int
    var err error
    glob, err = oneFunction()

I'd like to know if there is another way to set first value to global variable instead of creating a new one?

No. Your example that declares var err error is the idiomatic way to do what you want.