go lang defer runtime error code example

Example 1: the go blog defer panic recover

Calling g.
Printing in g 0
Printing in g 1
Printing in g 2
Printing in g 3
Panicking!
Defer in g 3
Defer in g 2
Defer in g 1
Defer in g 0
panic: 4

panic PC=0x2a9cd8
[stack trace omitted]

Example 2: the go blog defer panic recover

func CopyFile(dstName, srcName string) (written int64, err error) {
    src, err := os.Open(srcName)
    if err != nil {
        return
    }

    dst, err := os.Create(dstName)
    if err != nil {
        return
    }

    written, err = io.Copy(dst, src)
    dst.Close()
    src.Close()
    return
}