Why Does Go Flag 'Declared but Not Used' Variables as Errors?

Understanding the "Declared but not used" Error in Go

In Go, it is considered an error to declare a variable without using it. This is because Go's compiler checks for未使用代码，并且认为它们是多余的。

Case Study: Unused Variable

Consider the following code:

var partial string

for i, request := range requestVec {
    if i == (len(requestVec)-1) && !strings.Contains(request, "\r\n\r\n") {
        partial = request
        break
    }
}

In this code, the partial variable is declared within the global scope and assigned a value within the if statement. However, it is never used outside of the loop. The compiler therefore detects the partial declaration as unused and flags it as an error.

Resolution: Using Unused Variables

To resolve the "Declared but not used" error for unused variables, you can simply add code that utilizes the variable.

var partial string

for i, request := range requestVec {
    if i == (len(requestVec)-1) && !strings.Contains(request, "\r\n\r\n") {
        partial = request
        break
    }
}

fmt.Println(partial) // Utilizes `partial` in this line

In this modified code, the partial variable is now used within the fmt.Println statement, making it valid and removing the error.

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