Why does `if` change the scope of this variable?

If I have such a thing

Case 1:

if str, err := m.something(); err != nil {
        return err
    }

fmt.println(str)  //str is undefined variable

Case 2:

str, err := m.something(); 

fmt.println(str)  //str is ok

My question is why does the scope of the variable str change when used in this format

if str, err := m.something(); err != nil {
        return err
        //str scope ends
    }

Correct answer

Because the if statement (and for and switch) isImplicit blocks, according to the language specification, := is used for declarations and assignments. If you want str to be available after if, you can declare the variable first and then assign it a value in the if statement:

var s string
var err error

if str, err = m.something(); err != nil
// ...

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