Hi, Go's backwards compatibility guarantee is fantastic, but only applies to the language, not the standard library. How to I cause a build-time failure if someone tries to build my project with a too-old Go version?
I have a Go project that uses (or would like to use) a few features introduced in the standard library more recently, e.g. the %w verb in fmt.Errorf for wrapping errors (introduced in Go 1.13 <https://golang.org/doc/go1.13#error_wrapping>), and a fix to the text/template library (merged for Go 1.14 <https://github.com/golang/go/issues/34483>). The nature of these features and fixes mean that my code will compile and build fine, but will fail at runtime when a codepath that relies on the feature or fix is executed, which will result in a late, weird error. I would like an early, loud failure at build time instead. What's the best way to achieve this? As far as I can tell, there are a few options: The Go version can be determined by either the runtime.Version() function or by the presence of build flags (e.g. go1.13, go1.14, etc.). Calling runtime.Version() cannot result in a build time error (it can only be called once the code is running, which can only happen after a successful build) but could be used in either a test (so the old Go version gets caught when "go test" is run) or in an init() function to (say) panic on startup when tests or the program are run. This would look something like: import "runtime" func init() { if runtime.Version() < "1.13" { // string comparisons are not a good way to compare version strings, but you get the idea panic("go version too old") } } I can create a Go file with build flags that is only built on older versions of Go, something like: // +build !go1.13 build with go 1.13 or later // this is deliberately not valid go syntax This causes an error if built with an earlier version of Go than 1.13, but the error message isn't very intuitive (something like "filename.go:3:1: expected 'package', found build") and the invalid Go syntax might confuse other Go tooling which tends to assume that every .go file contains more-or-less valid Go code. Please note that I want to use these Go standard library features and fixes and provide an early, loud warning if they are not available. I know that I can use build flags to provide different code to different Go versions, but if I do that then I still have to maintain code for older Go versions. The core of this question is: how do I get a build error if my Go version is too old? What's the recommended way to ensure a minimum Go version at build time? One of the above suggestions or another way? Many thanks, Tom -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/7c9f2948-4187-4ccf-aebe-c524965a8be4%40googlegroups.com.
