Why Does My Go Code Show 'err declared but not used' Even Though I Use `err` in a Loop?

Understanding the "err declared but not used" Compile Error in Go

In Go, you may encounter a compile error stating "err declared but not used." This error typically arises when you declare a variable without assigning or utilizing it in your code. However, in your case, you have used the variable err within a for loop, but the compiler still reports the error.

Shadowing in Go

The issue lies in variable shadowing. In Go, the short variable declaration (using the := operator) creates a new variable with the same name as an existing variable in the same scope. This is distinct from variable assignment using the = operator, which modifies the value of an existing variable.

In your code, the err variable declared outside the for loop is shadowed by the err variable declared within the loop. This means that the err variable used in the for loop is a new variable that is independent of the one declared outside the loop. Consequently, the compiler detects that the err variable outside the loop is never used.

Resolving the Error

To avoid this shadowing issue, you can use the following approaches:

• Use a different name: Give the err variable inside the for loop a different name, such as loopErr.
• Use variable assignment: Instead of declaring a new err variable inside the loop, assign the value from the err variable outside the loop, such as err := err.

By making these adjustments, you can eliminate the shadowing and ensure that the err variable outside the loop is utilized as intended.

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