Weird Problem panic: runtime error: invalid memory address or nil pointer dereference

[virtue...@gmail.com]

I have simple go code as below, it returned the error as in " title " while executing, given the fact that /root/a.csv exists, and super user is executing go run a.go

Another problem is , if i removed println(fileInfo), it reported fileInfo declared and not used, am i not using it in the next line ? println(fileInfo.Size())??? This is very confusing 

package main

import(

"os"

)

func main() {

        var fileInfo os.FileInfo

        if fileInfo, err := os.Stat("/root/a.csv"); err != nil {

println(fileInfo)

        }

        println(fileInfo.Size())

        return

}

[Shawn Milochik]

The problem is that fileInfo is being shadowed by the := syntax. Outside the "if" block, fileInfo is nil again. If you replace the := with = and add "var err error" above, it will work.

[gp...@appliedgo.net]

In defense of the := syntax, the shorthand operator alone does not cause the problem, but only in combination with the if block creating a new scope. Try

    fileInfo, err := os.Stat("/...")

    if err != nil {

and the panic will also be gone. 

I never use the "if <assignment>; <condition>" syntax because I find it too convoluted. The shadowing problem is another good reason for not using that syntax.