What is xmlsig?

This is a Go library that lets you digitally sign XML documents. Think of it like adding a tamper-proof seal to a document, anyone who receives it can verify that you created it and that nobody has altered it since you signed it. The library works by taking an XML document (the structured data format that many business systems use) and a digital certificate (which proves your identity), then creating a cryptographic signature that gets attached to the document. When someone opens that signed document later, they can check the signature to confirm it really came from you and hasn't been modified. The key thing is that this library is designed to work with XML documents you've already created in Go using Go's built-in tools, so you don't need to install extra software or link to external C libraries. You'd use this if you're building a Go application that needs to produce signed XML, for example, a banking system that exchanges documents with other banks, a government system filing official records, or any integration where you need proof that a document is authentic and unchanged. Instead of having to call out to an external signing tool or dealing with complex certificate management, you can just load your certificate file and create signatures right in your Go code. One practical limitation worth noting: the library is designed specifically for XML you generate yourself through Go, not for signing arbitrary XML documents from unknown sources. This tradeoff keeps the library simple and fast, since properly handling all the quirks of other people's XML formatting (a process called canonicalization) is considerably more work. For most real-world Go applications, this is fine, you're usually signing documents your own code created anyway.