Get rid of dependencies

[michelseiler]

It would be nice if this package reduce the dependencies.

Package github.com/pkg/errors is used in errors/errors.go:

• pkg_errors.Errorf(Prefix+format, a...) could be replaced with fmt.Errorf(Prefix+format, a...)
• pkg_errors.New(Prefix + text) could be replaced with fmt.Errorf(Prefix + text)

Package golang.org/x/exp is used in client_sub.go and debug/debug.go for slices:

• It could perhaps be replaced by the standard library function slices.Contains() when Bumping GO version to 1.21.

[michelseiler]

Thanks! Should i write another issue for the golang.org/x/exp package since this is not resolved by PR https://github.com/gopcua/opcua/pull/731?

[kung-foo]

As I wrote (just now) in https://github.com/gopcua/opcua/pull/721, we are going to hold at Go 1.20 due to compatibility issues which means the slices.Contains generic function isn't available.

[michelseiler]

Thanks for the clarification