Errata

setx GOPATH %USERPROFILE%\go
setx path "%path%;%USERPROFILE%\bin"

In the second line, the correct line should be like this:
setx path "%path%;%GOPATH%\bin

Dear Sir,

The book OREILLY Learning Go really helped me in learning the concepts, but I found the tool go lint is deprecated in the beginning of 2021 and it needs corrections in the next edition of Learning Go book. remove the complete concept on go lint mentioned in this book as it will not work on existing code. reference page number - 28 and 29 some lines of the book.
sending these details so that it will help the author for further corrections. :)

reference link - https://pkg.go.dev/golang.org/x/lint#section-readme

The text mentions an interface but the code uses a different one. Here the text mentions io.Writer implements io.WriterTo and io.Reader implements io.ReaderFrom. But the code uses the other way around. src which is an instance of io.Reader is checked for WriterTo and dst which is an instance of io.Writer is checked for ReaderFrom.

"This function has two parameters of types io.Writer
and io.Reader and calls the io.copyBuffer function to do its work. If the io.Writer
parameter also implements io.WriterTo, or the io.Reader parameter also implements
io.ReaderFrom, most of the work in the function can be skipped:"
func copyBuffer(dst Writer, src Reader, buf []byte) (written int64, err error) {
// If the reader has a WriteTo method, use it to do the copy.
// Avoids an allocation and a copy.
if wt, ok := src.(WriterTo); ok {
return wt.WriteTo(dst)
}
// Similarly, if the writer has a ReadFrom method, use it to do the copy.
if rt, ok := dst.(ReaderFrom); ok {
return rt.ReadFrom(src)
}